PowerPC undefweak handling

PowerPC undefweak handling

This patch fixes a number of cases where -z nodynamic-undefined-weak
was not effective in preventing dynamic relocations or linkage stubs.

	* elf32-ppc.c (UNDEFWEAK_NO_DYNAMIC_RELOC): Define.
	(ppc_elf_select_plt_layout, ppc_elf_tls_setup): Use it.
	(ppc_elf_adjust_dynamic_symbol, allocate_dynrelocs): Likewise.
	(ppc_elf_relocate_section): Likewise.  Delete silly optimisation
	for undef and undefweak dyn_relocs.
	* elf64-ppc.c (UNDEFWEAK_NO_DYNAMIC_RELOC): Define.
	(ppc64_elf_adjust_dynamic_symbol, ppc64_elf_tls_setup): Use it.
	(allocate_got, allocate_dynrelocs): Likewise.
	(ppc64_elf_relocate_section): Likewise.