PowerPC64 __tls_get_addr_desc

This implements register saving and restoring in the __tls_get_addr
call stub, so that when glibc supports the optimized tls call stub gcc
can generate code that assumes only r0, r12 and of course r3 are
changed on a __tls_get_addr call.  When gcc expects __tls_get_addr
calls to preserve registers the call will be to __tls_get_addr_desc,
which will be translated by the linker to a call to __tls_get_addr_opt.

bfd/
	* elf64-ppc.h (struct ppc64_elf_params): Add no_tls_get_addr_regsave.
	* elf64-ppc.c (struct ppc_link_hash_table): Add tga_desc and
	tga_desc_fd.
	(is_tls_get_addr): Match tga_desc and tga_desc_df too.
	(STDU_R1_0R1, ADDI_R1_R1): Define.
	(tls_get_addr_prologue, tls_get_addr_epilogue): New functions.
	(ppc64_elf_tls_setup): Set up tga_desc and tga_desc_fd.  Indirect
	tga_desc_fd to opt_fd, and tga_desc to opt.  Set
	no_tls_get_addr_regsave.
	(branch_reloc_hash_match): Add hash3 and hash4.
	(ppc64_elf_tls_optimize): Handle tga_desc_fd and tga_desc too.
	(ppc64_elf_size_dynamic_sections): Likewise.
	(ppc64_elf_relocate_section): Likewise.
	(plt_stub_size, build_plt_stub): Likewise.  Size regsave
	__tls_get_addr stub.
	(build_tls_get_addr_stub): Build regsave __tls_get_addr stub and
	eh_frame.
	(ppc_size_one_stub): Handle tga_desc_fd and tga_desc too.  Size
	eh_frame for regsave __tls_get_addr.
gas/
	* config/tc-ppc.c (parse_tls_arg): Handle tls arg for
	__tls_get_addr_desc and __tls_get_addr_opt.
ld/
	* emultempl/ppc64elf.em (ppc64_opt, PARSE_AND_LIST_LONGOPTS),
	(PARSE_AND_LIST_OPTIONS, PARSE_AND_LIST_ARGS_CASES): Support
	--tls-get-addr-regsave and --no-tls-get-addr-regsave.
	(params): Init new field.
	* ld.texi (--tls-get-addr-regsave, --no-tls-get-addr-regsave):
	Document.
	* testsuite/ld-powerpc/tlsdesc.s,
	* testsuite/ld-powerpc/tlsdesc.d,
	* testsuite/ld-powerpc/tlsdesc.wf,
	* testsuite/ld-powerpc/tlsdesc2.d,
	* testsuite/ld-powerpc/tlsdesc2.wf,
	* testsuite/ld-powerpc/tlsexenors.d,
	* testsuite/ld-powerpc/tlsexenors.r,
	* testsuite/ld-powerpc/tlsexers.d,
	* testsuite/ld-powerpc/tlsexers.r,
	* testsuite/ld-powerpc/tlsexetocnors.d,
	* testsuite/ld-powerpc/tlsexetocrs.d,
	* testsuite/ld-powerpc/tlsexetocrs.r,
	* testsuite/ld-powerpc/tlsopt6.d,
	* testsuite/ld-powerpc/tlsopt6.wf: New.
	* testsuite/ld-powerpc/powerpc.exp: Run new tests.