support stabs on mach-o GAS.

support stabs on mach-o GAS.

bfd:

	* mach-o.c (bfd_mach_o_mangle_symbols): Put in the section index
	for stabd symbols.
	(bfd_mach_o_primary_symbol_sort_key): Adjust for stabs.
	(bfd_mach_o_cf_symbols): Likewise.

gas:

	* config/obj-macho.c (obj_macho_process_stab): New.
	* config/obj-macho.h (OBJ_PROCESS_STAB): Define.
	(obj_macho_process_stab): Declare.