[C++ PATCH] Reserve a decl_lang bit

[C++ PATCH] Reserve a decl_lang bit

https://gcc.gnu.org/ml/gcc-patches/2019-09/msg00365.html
	Reserve TREE_LANG_FLAG_3 for modules.
	gcc/cp/
	* cp-tree.h (DECL_CONSTRUCTION_VTABLE_P): Delete.
	(DECL_NON_TRIVIALLY_INITIALIZED_P): Move to TREE_LANG_FLAG_6.
	* class.c (build_ctor_vtbl_group): Don't set
	DECL_CONSTRUCTION_VTABLE_P.
	* decl2.c (determine_visibility_from_class): Don't check
	DECL_CONSTRUCTION_VTABLE_P anymore.

From-SVN: r275455