re PR c++/70594 (-fcompare-debug failure)

re PR c++/70594 (-fcompare-debug failure)

	PR c++/70594
	* constexpr.c (constexpr_call_table): Preserve in GC.
	(struct fundef_copy, struct fundef_copies_table_t):	Delete.
	(fundef_copies_table): Preserve in GC. Change to pointer to
	tree->tree hash.
	(maybe_initialize_fundef_copies_table): Adjust.
	(get_fundef_copy): Return a TREE_LIST.  Use non-inserting search.
	(save_fundef_copy): Adjust for a TREE_LIST.
	(cxx_eval_call_expression): Adjust for a fundef_copy TREE_LIST.
	(fini_constexpr): New.
	* cp-tree.h (fini_constexpr): Declare.
	* decl2.c (c_parse_final_cleanups): Call fini_constexpr.

Co-Authored-By: Nathan Sidwell <nathan@acm.org>
From-SVN: r235033