1.0.29.24: preserve docstrings for local and anonymous functions

  Based on patch by Lessie Polzer:

* Rename SIMPLE-FUN-XREFS to SIMPLE-FUN-INFO. Slot holds the docstring
  and/or XREF vector for the function. This saves space in the common
  case of no dostring -- the patch actually ends up shrinking
  sbcl.core a bit.

* Teach the compiler how to grab the docstrings from LAMBDAs and how
  to preserve them for the lambdas constructed for FLET and LABELS
  functions.

* Store COMPILER-MACRO documentation in the COMPILER-MACRO-FUNCTION.

* Store macro documentation in the MACRO-FUNCTION.

* Nuke (INFO :FUNCTION :DOCUMENTATION).