* m68k-tdep.h (enum struct_return): Define.

	* m68k-tdep.h (enum struct_return): Define.
	(struct gdbarch_tdep): Add struct_return.
	* m68k-tdep.c (m68k_push_dummy_call): Non-scalars bigger than 4
	bytes are padded to the right, not to the left.  Pass struct value
	address in register %a1, not on stack.
	(m68k_use_struct_convention): New function.
	(m68k_gdbarch_init): Set use_struct_convention.  Initialize
	struct_return in tdep to pcc_struct_return.
	* m68klinux-tdep.c (m68k_linux_init_abi): Set struct_return to
	reg_struct_return.