* libguile/hashtab.c:
* libguile/hashtab.h: Reimplement the weak hash table implementation in
terms of weak tables. All is well except for the horrific hack for
hashx tables.
* libguile/weak-table.h:
* libguile/weak-table.c (scm_make_weak_key_hash_table)
(scm_make_weak_value_hash_table, scm_make_doubly_weak_hash_table)
(scm_weak_key_hash_table_p, scm_weak_value_hash_table_p)
(scm_doubly_weak_hash_table_p): Move these definitions here.
* libguile/weak-table.c:
* libguile/weak-table.h: New files, implementing open-addressed weak
hash tables, similar to the implementation of weak sets. This will
let us remove weak pairs.
* libguile.h:
* libguile/Makefile.am:
* libguile/evalext.c:
* libguile/gc.c:
* libguile/init.c:
* libguile/print.c:
* libguile/tags.h: Update all the pieces for the new files and tc7.
