PowerPC notoc linkage stubs

PowerPC notoc linkage stubs

Use pcrel addressing instructions in linkage stubs.

bfd/
	* elf64-ppc.c: Comment on powerxx _notoc stub variants.
	(LI_R11_0, LIS_R11, ORI_R11_R11_0, SLDI_R11_R11_34): Define.
	(PADDI_R12_PC, PLD_R12_PC, D34, HA34): Define.
	(struct ppc_link_hash_table): Add powerxx_stubs.
	(ppc64_elf_check_relocs): Set powerxx_stubs.
	(build_powerxx_offset, size_powerxx_offset),
	(num_relocs_for_powerxx_offset),
	(emit_relocs_for_powerxx_offset): New functions.
	(plt_stub_size): Size powerxx stubs.
	(ppc_build_one_stub): Emit powerxx stubs.
	(ppc_size_one_stub): Size powerxx stubs.  Omit .eh_frame for
	powerxx stubs.
ld/
	* testsuite/ld-powerpc/notoc2.d,
	* testsuite/ld-powerpc/notoc2.s: New test.
	* testsuite/ld-powerpc/powerpc.exp: Run it.