ppc476 gas warn on data in code sections

	* config/tc-ppc.c (warn_476, last_insn, last_seg, last_subseg):
	New static vars.
	(md_longopts, md_parse_option, md_show_usage): Add --ppc476-workaround.
	(ppc_elf_cons_fix_check): New function.
	(md_assemble): Set last_insn, last_seg, last_subseg.
	(ppc_byte, md_apply_fix): Handle warn_476.
	* config/tc-ppc.h (TC_CONS_FIX_CHECK): Define.
	(ppc_elf_cons_fix_check): Declare.
	* read.c (cons_worker): Invoke TC_CONS_FIX_CHECK.