* weaks.c (scm_scan_weak_vectors): move the calculation of the

	* weaks.c (scm_scan_weak_vectors): move the calculation of the
	`weak_keys' and `weak_values' flags out of the inner loop.

	* guardians.c: (greedily_guarded_prop): deleted.
	(greedily_guarded_whash): new variable.  a doubly-weak hash table
	used to keep the "greedily hashed" object property.  the previous
	implementation (via primitive object properties) was incorrect due
	to its only-the-key-is-weak semantics.
	(scm_guard, get_one_zombie, scm_init_guardians): use/init
	`greedily_guarded_whash'.