PR middle-end/97879 - ICE on invalid mode in attribute access

gcc/c-family/ChangeLog:

	PR middle-end/97879
	* c-attribs.c (handle_access_attribute): Handle ATTR_FLAG_INTERNAL.
	Error out on invalid modes.

gcc/c/ChangeLog:
	PR middle-end/97879
	* c-decl.c (start_function): Set ATTR_FLAG_INTERNAL in flags.

gcc/ChangeLog:

	PR middle-end/97879
	* tree-core.h (enum attribute_flags): Add ATTR_FLAG_INTERNAL.

gcc/testsuite/ChangeLog:

	PR middle-end/97879
	* gcc.dg/attr-access-3.c: New test.