Implementation of new, very efficient EQ?-hash tables. These tables

Implementation of new, very efficient EQ?-hash tables.  These tables
use address hashing, automatically rehash themselves when garbage
collections move their keys around, and automatically clean themselves
as their keys are reclaimed by the GC.  MAKE-EQ-HASH-TABLE is used to
create these tables; MAKE-OBJECT-HASH-TABLE and MAKE-SYMBOL-HASH-TABLE
are now aliases for this new procedure.

HASH-TABLE/SIZE now returns the "usable size" of the table, as claimed
by the documentation, rather than the "physical size".

New enumeration procedures HASH-TABLE->ALIST, HASH-TABLE/KEY-LIST, and
HASH-TABLE/DATUM-LIST.