elf64-ppc.c memory leaks

I've freed htab->relr in two places, first when we're done with it
in ppc64_elf_build_stubs, and also when freeing the hasn table to
catch cases where the linker exits early due to errors.

	* elf64-ppc.c (ppc64_elf_link_hash_table_free): Free htab->relr.
	(ppc64_elf_build_stubs): Also free it here.
	(ppc_add_stub): Copy stub_name when creating..
	(ppc64_elf_size_stubs): ..and always free stub_name.
	(opd_entry_value): Free sym.
	(ppc_build_one_stub): bfd_alloc stub sym name.
	(build_global_entry_stubs_and_plt): Likewise.
	(ppc64_elf_setup_section_lists): bfd_zalloc htab->sec_info.