Remove class cache_map and use ggc hash_maps instead (PR c++/70452)

Remove class cache_map and use ggc hash_maps instead (PR c++/70452)

gcc/cp/ChangeLog:

	PR c++/70452
	* cp-tree.h (class cache_map): Remove.
	* constexpr.c (cv_cache): Change type to
	GTY((deletable)) hash_map<tree, tree> *.
	(maybe_constant_value): Adjust following the change to cv_cache.
	(clear_cv_cache): New static function.
	(clear_cv_and_fold_caches): Use it.
	* cp-gimplify.c (fold_cache): Change type to
	GTY((deletable)) hash_map<tree, tree> *.
	(clear_fold_cache): Adjust following the change to fold_cache.
	(cp_fold): Likewise.

From-SVN: r234732