Missing a clause in ECASE in %DEFINE-SYMBOL-MACRO
Fix discrepancy in how MACROEXPAND-1 calls the expander for symbols.
INFO :SETF :EXPANDER/:INVERSE can't both return T as their second value.

Setting an INFO to NIL was a technique that made some degree of sense
when the globaldb didn't allow clearing, but clearing is more sensible.

The unrelated QUIETLY-ASSIGN-SETF-MACRO function will be used
in a subsequent change.
Make fewer special references to *BYTE-BUFFER*
Eliminate most bootstrap warnings and make #+sb-show less noisy.

The number of lines of /show output to wade through before saving
of sbcl.core is down to about 197K.
The kludge in DEFUN WARN can soon be removed, perhaps already.