PR c++/70029 - ICE with ref-qualifier and -flto

PR c++/70029 - ICE with ref-qualifier and -flto

	PR c++/70029 - ICE with ref-qualifier and -flto
gcc/
	* langhooks.h (struct lang_hooks_for_types): Add
	copy_lang_qualifiers.
	* attribs.c (build_type_attribute_qual_variant): Use it.
	* langhooks-def.h (LANG_HOOKS_COPY_LANG_QUALIFIERS): Default to
	NULL.
	(LANG_HOOKS_FOR_TYPES_INITIALIZER): Use it.
	* tree.c (verify_type): Re-enable TYPE_CANONICAL main variant check.
gcc/cp/
	* tree.c (cxx_copy_lang_qualifiers): New.
	* cp-tree.h: Declare it.
	* cp-objcp-common.h: Define LANG_HOOKS_COPY_LANG_QUALIFIERS.

From-SVN: r251911