part 3 of darwin64 PPC ABI changes

part 3 of darwin64 PPC ABI changes

	* config/rs6000/rs6000.c (rs6000_override_options):
	Use TARGET_MACHO inline, move darwin_one_byte_bool from here...
	... to darwin_rs6000_override_options.
	(rs6000_return_in_memory): Update preceding comment for darwin
	64 bit ABI.  Use TARGET_MACHO inline.
	(rs6000_darwin64_struct_check_p): New.
	(function_arg_advance): Use rs6000_darwin64_struct_check_p.
	(function_arg): Likewise.
	(rs6000_arg_partial_bytes): Likewise.
	(rs6000_function_value): Likewise.

From-SVN: r162635