reverse the order of relocs in mach-o gas output.

reverse the order of relocs in mach-o gas output.

gas:

	* config/obj-macho.c (obj_mach_o_reorder_section_relocs): New.
	* config/obj-macho.h (SET_SECTION_RELOCS): Define.
	(obj_mach_o_reorder_section_relocs): Declare.

gas/testsuite:

	* gas/all/redef2.d: Skip for Darwin.
	* gas/all/redef3.d: Likewise.
	* gas/all/weakref1.d: Likewise.
	* gas/macros/irp.d: Likewise.
	* gas/macros/repeat.d: Likewise.
	* gas/macros/rept.d: Likewise.
	* gas/macros/test2.d: Likewise.
	* gas/macros/vararg.d: Likewise.
	* gas/mach-o/macro-irp.d: New.
	* gas/mach-o/macro-repeat.d: New.
	* gas/mach-o/macro-rept.d: New.
	* gas/mach-o/macro-test2.d: New.
	* gas/mach-o/macro-vararg.d: New.
	* gas/mach-o/redef2.d: New.
	* gas/mach-o/redef3.d: New.