PowerPC64 EH info for _notoc linkage stubs

PowerPC64 EH info for _notoc linkage stubs

This patch generates EH info for the new _notoc linkage stubs, to
support unwinding from asynchronous signal handlers.  Unwinding
through the __tls_get_addr_opt stub was already supported, but that
was just a single stub.  With multiple stubs the EH opcodes need to be
emitted and sized when iterating over stubs, so this is done when
emitting and sizing the stub code.  Emitting the CIEs and FDEs is done
when sizing the stubs, as we did before in order to have the linker
generated FDEs indexed in .eh_frame_hdr.  I moved the final tweaks to
FDEs from ppc64_elf_finish_dynamic_sections to ppc64_elf_build_stubs
simply because it's tidier to be done with them at that point.

bfd/
	* elf64-ppc.c (struct map_stub): Delete tls_get_addr_opt_bctrl.
	Add lr_restore, eh_size and eh_base.
	(eh_advance, eh_advance_size): New functions.
	(build_tls_get_addr_stub): Emit EH info for stub.
	(ppc_build_one_stub): Likewise for _notoc stubs.
	(ppc_size_one_stub): Size EH info for stub.
	(group_sections): Init new map_stub fields.
	(stub_eh_frame_size): Delete.
	(ppc64_elf_size_stubs): Size EH info for stubs.  Set up dummy EH
	program for stubs.
	(ppc64_elf_build_stubs): Reinit new map_stub fields.  Set FDE
	offset to stub section here..
	(ppc64_elf_finish_dynamic_sections): ..rather than here.
ld/
	* testsuite/ld-powerpc/notoc.s: Generate some cfi.
	* testsuite/ld-powerpc/notoc.d: Adjust.
	* testsuite/ld-powerpc/notoc.wf: New file.
	* testsuite/ld-powerpc/powerpc.exp: Run "ext" and "notoc" tests
	as run_ld_link_tests rather than run_dump_test.