Support trampoline jumps on powerpc.

	Support trampoline jumps on powerpc.

	* grub-core/kern/dl.c (grub_dl_load_segments) [__powerpc__]: Follow
	__ia64__ path.
	(grub_dl_load_segments): Set mod->sz.
	(grub_dl_flush_cache): Flush whole space occupied by module, not just
	segments.
	* grub-core/kern/ia64/dl.c (nopm): Make const while on it.
	(jump): Likewise.
	* grub-core/kern/powerpc/dl.c (grub_arch_dl_get_tramp_got_size): New
	function.
	(trampoline): New struct.
	(trampoline_template): New const.
	(grub_arch_dl_relocate_symbols): Create trampolines on overflow.
	* include/grub/dl.h (grub_dl): Add sz element.
	[__powerpc__]: Follow __ia64__.
	(GRUB_ARCH_DL_TRAMP_ALIGN): Define on ppc.
	(GRUB_ARCH_DL_GOT_ALIGN): Likewise.
	(GRUB_ARCH_DL_TRAMP_SIZE): Likewise.
	(grub_arch_dl_get_tramp_got_size) [__powerpc__]: New proto.