primarily intending to integrate Colin Walter's O(N) map code and

primarily intending to integrate Colin Walter's O(N) map code and
fixing BUTLAST (but doing some other stuff too, since achieving the
primary objective involved a lot of inspecting other code):

another revision of MAP stuff, part I:
  * I switched over to code inspired by Colin Walters' O(N) MAP
    code (from the cmucl-imp mailing list 2000 Sep 02) for the
    general non-DEFTRANSFORM case.
  * HIGH-SECURITY-SUPPORT error checking logic goes away, pending
    part II
  * I made some  miscellaneous cleanups of old arity-1 code too.
  * The old MAP-FOR-EFFECT, MAP-TO-LIST, and MAP-TO-SIMPLE macros,
    and the old functions MAP-WITHOUT-ERRORCHECKING, and
    GET-MINIMUM-LENGTH-SEQUENCES go away.
  * The old #+!HIGH-SECURITY length-checking logic goes
    away, to be replaced by stuff in part II.
  * New O(N) functions %MAP-FOR-EFFECT, %MAP-TO-LIST, and
    %MAP-TO-VECTOR are added, and MAP is redefined in terms of them.
  * Add a note pointing out that since MAP-INTO has not been
    rewritten to take advantage of all the new mapping technology,
    it's still slow.
  * Delete no-longer-used ELT-SLICE macro.

another revision of MAP stuff, part II: Peter Van Eynde might go into
a killing frenzy, or at least his ansi-test suite will gnaw SBCL to
death, unless we raise type errors on length mismatches like
  (MAP '(SIMPLE-VECTOR 128) #'+ #(1 2) #(1 1)).
How to do this without clobbering efficiency? More DEFTRANSFORMs, I
think..
  * MAP becomes a wrapper around %MAP. %MAP doesn't do this
    kind of length checking, MAP does. The old DEFUN MAP,
    DEFKNOWN MAP, and DEFTRANSFORM MAP stuff all turns into
    corresponding definitions for %MAP. The wrapper is
    implemented both as a DEFUN MAP and a DEFTRANSFORM MAP.
  * Now make DEFTRANSFORM MAP smarter:
    ** If necessary, check at runtime that ARRAY-DIMENSION
       matches what we pull out of SPECIFIER-TYPE.
    ** No test is done when SPEED > SAFETY.
    ** No test is needed when we can tell at compile time that
       the result type doesn't specify the length of the result.
  * Also add the same kind of ARRAY-DIMENSION/SPECIFIER-TYPE runtime
    check to DEFUN MAP.
  * While I'm at it, since DEFTRANSFORM MAP needs to think hard about
    the type of the result anyway, it might as well declare what
    it's figured out (TRULY-THE) to benefit any code downstream.

Start playing with MAP regression tests. Add tests/assertoid.lisp to
support future regression tests.

Once I started using the QUIT :UNIX-CODE keyword argument in my test
cases, I could see that it isn't very mnemonic. So I changed it to the
more-descriptive name :UNIX-STATUS, leaving the old name supported but
deprecated.

Oops! The old DEFTRANSFORM MAP (now DEFTRANSFORM %MAP) should really
only be done when (>= SPEED SPACE), but it wasn't declared that way.

While looking for an example of a DEFTRANSFORM with &REST arguments
to use as a model for the code in the new DEFTRANSFORM from MAP to
%MAP, I noticed that the problem of taking a list of names and
generating a corresponding list of gensyms is solved in many different
places in the code, in several ways. Also, the related problem of just
creating a list of N gensyms is solved in several places in in the
code. This seems unnecessarily error-prone and wasteful, so I went
looking for such cases and turned them into calls to MAKE-GENSYM-LIST.

another revision of MAP stuff, part III:
  * Search for 'map' in the output from clocc ansi-tests/tests.lisp,
    to check that the new MAP code isn't too obviously broken.
  * Add some regression tests in test/map.impure.lisp.

Oops! The various %MAP-..-ARITY-1 helper functions expect a function
argument, but DEFTRANSFORM MAP can call them passing them a function
name instead.
  * Change the helper functions so that they can handle
    function names as arguments.
  * Define %COERCE-CALLABLE-TO-FUNCTION to help with this. Note that
    this seems to be what %COERCE-NAME-TO-FUNCTION meant long ago,
    judging from DEFTRANSFORM %COERCE-NAME-TO-FUNCTION; so
    appropriate that DEFTRANSFORM for %COERCE-CALLABLE-TO-FUNCTION.
  * Use %COERCE-CALLABLE-TO-FUNCTION elsewhere that expressions
    involving %COERCE-NAME-TO-FUNCTION were used previously.

deleted the old commented-out version of DEFMACRO HANDLER-CASE
(since it was marked "Delete this when the system is stable.":-)

deleted the old commented-out version of GEN-FORMAT-DEF-FORM,
since it was supposed to be safe to do so after sbcl-0.6.4

I removed the apology for not using PRINT-OBJECT everywhere in the
printer from the bugs list in the man page, since it seems to be
rather tricky to construct a test case which exposes the system's
non-PRINT-OBJECT-ness without the test case itself violating the ANSI
spec.

I updated, cleaned up, or removed outright some other outdated or
confusing entries in the BUGS file and from the bugs list on the man
page.

Now that BUTLAST no longer blows up on the new problem cases a la
(BUTLAST NIL -1), I wonder whether I could stop it from blowing
up on the old problem cases a la (BUTLAST NIL)? It looks like
a compiler problem, since the interpreted definition of BUTLAST works,
even though the compiled one doesn't. In fact, it's a declaration
problem, since LENGTH is set to -1 when LIST=NIL, but is declared
as an INDEX. (Of course it's likely also a compiler problem, since
the compiler is supposed to signal type errors for this kind of
declaration error.) I fixed the misdeclaration, and noted the
possible compiler bug in BUGS.

After writing the new revised weird type declarations for the
not-necessarily positive LENGTH, and writing explanatory comments,
  ;; (Despite the name, LENGTH can be -1 when when LIST is an ATOM.)
for each of the cut-and-pasted (LET ((LENGTH ..)) ..) forms in BUTLAST
and NBUTLAST, I said "screw it" -- no, that's not it, I quoted Martin
Fowler and Kent Beck: "If you see the same code structure in more than
one place, you can be sure that your program will be better if you
find a way to unify them," and "It's surprising how often you look at
thickly commented code and notice that the comments are there because
the code is bad." So I just rewrote BUTLAST and NBUTLAST. Hopefully
the new versions will be better-behaved than the old ones.

Now that the INDEX type is used in DEFUN MAKE-GENSYM-LIST, which
belongs in early-extensions.lisp, INDEX should be defined before
early-extensions.lisp, i.e. earlier than its current definition in
early-c.lisp. Move it to early-extensions.lisp. Then to make that
work, since DEF!TYPE is used to define INDEX, defbangtype.lisp needs
to precede early-extensions.lisp in stems-and-flags.lisp-expr; so move
it. Also, INDEX is defined in terms of SB!XC:ARRAY-DIMENSION-LIMIT, so
early-array.lisp needs to move before the new location of
defbangtype.lisp. And then early-vm.lisp needs to move before that, so
I might as well move the rest of the early-vm-ish stuff back too. And
then DEFTYPE is used before deftype.lisp, so I need to change DEFMACRO
DEF!TYPE to DEF!MACRO DEF!TYPE, so I need to move defbangmacro.lisp
before deftype.lisp. (This is like a trip down memory lane to the
endless tweaks and recompiles it took me to find and unravel the
twisted order dependencies which make CMU CL unbootstrappable. Ah,
those were the days..:-)

The DEFTYPEs for INDEX and POSN in early-assem.lisp duplicate
the functionality of the SB-KERNEL:INDEX type.
  * Change uses of the SB-ASSEM::POSN type to uses of the INDEX type.
  * Delete the SB-ASSEM::POSN type and the SB-ASSEM::MAX-POSN constant.
  * Move SB-KERNEL:INDEX into SB-INT, since it's not really
    just a kernel-level thing, but makes sense for implementing
    user-level stuff in SB-INT and SB-EXT and SB-C (and SB-ASSEM).
  * Grep for all '[a-z]:+index[^-a-z]' and rename them (or just
    remove prefixes) to match new SB-INT-ness of INDEX.
  * Make the SB-ASSEM package use the SB-INT package; delete
    the SB-ASSEM::INDEX type and SB-ASSEM::MAX-INDEX constant.
    And since as a rule anything which can see SB-INT deserves
    to see SB-EXT too, make SB-ASSEM use SB-EXT as well.