1.0.14.34: slightly less and slightly faster constraint propagation

1.0.14.34: slightly less and slightly faster constraint propagation

 * For negated EQL constaints, don't cons up multiple MEMBER-TYPE
   instances during a single pass through CONSTRAIN-REF-TYPE:
   accumulate a single XSET, and turn it into a MEMBER-TYPE only at
   the end.

 * Don't construct (NOT (MEMBER ...TON-OF-SYMBOLS...)) types at all,
   unless SPEED > COMPILATION speed. Knowing that a variable is not
   in a set of symbols is seldom useful, and compiling large CASE
   statements with symbols as keys can end up spending huge amounts
   of time just building these sets.

 * Adjust FD-STREAMS to use an ECASE in the single place in SBCL where
   without the aforementioned constraint propagation the compiler is
   not able to determine sufficiently constrain the result type.  (Not
   needed since the build has SPEED > COMPILATION-SPEED, but keeps
   things non-brittle.)