ppc64 out-of-line register save/restore functions

ppc64 out-of-line register save/restore functions

Don't emit long branch or plt branch stubs to save/restore functions.
Copy them instead.  The problem is that plt branch stubs currently
trash r12, one of the parameters to some of the save/restore
functions, and there is no free register available to use instead of
r12.

6f20ed8a is prerequisite for this patch.

	PR 18878
	* elf64-ppc.c (ARRAY_SIZE): Define.  Use throughout.
	(enum ppc_stub_type): Add ppc_stub_save_res.
	(struct map_stub): Add "next" and "needs_save_res".
	(struct ppc_link_hash_entry): Add "save_res" flag.
	(struct ppc_link_hash_table): Add "group".
	(sfpr_define): Add stub_sec param.  Define symbol in stub_sec if
	stub_sec is non-null.  Set "save_res".
	(save_res_funcs): Make file scope, rename from funcs.  Adjust uses.
	(ppc64_elf_adjust_dynamic_symbol): Prohibit plt call to save_res syms.
	(ppc_build_one_stub): Handle ppc_stub_save_res.
	(ppc_size_one_stub): Set stub type to ppc_size_one_stub on finding
	stub for linker defined save_res sym.
	(group_sections): Init new fields of struct map_stub.
	(ppc64_elf_size_stubs): Reserve space for save/restore func copy.
	(ppc64_elf_build_stubs): Copy save/restore funcs to groups.  Emit
	alias syms too.
	(ppc64_elf_relocate_section): Set destination for ppc_stub_save_res.