aix: implement TLS relocation for gas and ld

aix: implement TLS relocation for gas and ld

Add support for TLS in XCOFF. Amongst the things done by this commit:
 - Update XCOFF auxialiary header to match new version and allow TLS
   sections.
 - Add TLS sections (.tdata and .tbss) support in gas and ld.
 - Add support for the TLS relocations in gas and ld.
   Two different types BFD_RELOC are created for PPC and PPC64 as
   the size is a pointer, thus distinct in 32 or 64bit.

The addresses given by ld to .tdata and .tbss is a bit special. In
XCOFF, these addresses are actually offsets from the TLS pointer
computed at runtime. AIX assembly and linker does the same. In
top of that, the .tdata must be before .data (this is mandatory for AIX
loader). Thus, the aix ld script is recomputing "." before .data to restore
its original value. There might be a simpler way, but this one is working.

Optimisation linked to TLS relocations aren't yet implemented.

bfd/
	* reloc.c (BFD_RELOC_PPC_TLS_LE, BFD_RELOC_PPC_TLS_IE,
	BFD_RELOC_PPC_TLS_M, BFD_RELOC_PPC_TLS_ML, BFD_RELOC_PPC64_TLS_GD,
	BFD_RELOC_PPC64_TLS_LD, BFD_RELOC_PPC64_TLS_LE,
	BFD_RELOC_PPC64_TLS_IE, BFD_RELOC_PPC64_TLS_M,
	BFD_RELOC_PPC64_TLS_ML): New relocations.
	* bfd-in2.h: Regenerate.
	* libbfd.h: Regenerate.
	* coff-rs6000.c (xcoff_calculate_relocation): Call
	xcoff_reloc_type_tls for TLS relocations.
	(xcoff_howto_table): Implement TLS relocations.
	(_bfd_xcoff_reloc_type_lookup): Add cases TLS relocations.
	(xcoff_reloc_type_tls): New function.
	* coff64-rs6000.c (xcoff_calculate_relocation): Likewise.
	(xcoff_howto_table): Likewise.
	(_bfd_xcoff_reloc_type_lookup): Likewise.
	* coffcode.h (sec_to_styp_flags): Handle TLS sections.
	(styp_to_sec_flags): Likewise.
	(coff_compute_section_file_positions): Avoid file offset
	optimisation for .data when the previous section is .tdata.
	(coff_write_object_contents): Handle TLS sections.
	* coffswap.h (coff_swap_aouthdr_out): Add support for
	new fields in aouthdr.
	* libxcoff.h (xcoff_reloc_type_tls): Add prototype.
	* xcofflink.c (xcoff_link_add_symbols): Handle XMC_UL.
	(xcoff_need_ldrel_p): Add cases for TLS relocations.
	(xcoff_create_ldrel): Add l_symndx for TLS sections.
gas/
	* config/tc-ppc.c (ppc_xcoff_text_section, ppc_xcoff_data_section,
	(ppc_xcoff_bss_section, ppc_xcoff_tdata_section,
	(ppc_xcoff_tbss_section): New variables.
	(ppc_text_subsegment, ppc_text_csects, ppc_data_subgments,
	(ppc_data_csects): Removed.
	(ppc_xcoff_section_is_initialized, ppc_init_xcoff_section,
	ppc_xcoff_parse_cons): New functions.
	(md_being): Initialize XCOFF sections.
	(ppc_xcoff_suffix): Add support for TLS relocations
	(fixup_size, md_apply_fix): Add support for new BFD_RELOC.
	(ppc_change_csect): Handle XMC_TL, XMC_UL.  Correctly, add XMC_BS
	to .bss section.  Handle new XCOFF section variables.
	(ppc_comm): Likewise.
	(ppc_toc): Likewise.
	(ppc_symbol_new_hook): Likewise.
	(ppc_frob_symbol): Likewise.
	(ppc_fix_adjustable): Add tbss support.
	* config/tc-ppc.h (TC_PARSE_CONS_EXPRESSION): New define.
	(ppc_xcoff_parse_cons): Add prototype.
	(struct ppc_xcoff_section): New structure.
ld/
	* emultempl/aix.em: Ensure .tdata section is removed
	if empty, even with -r flag.
	* scripttempl/aix.sc: Handle TLS sections.
	* testsuite/ld-powerpc/aix52.exp: Add new tests.
	* testsuite/ld-powerpc/aix-tls-reloc-32.d: New test.
	* testsuite/ld-powerpc/aix-tls-reloc-64.d: New test.
	* testsuite/ld-powerpc/aix-tls-reloc.ex: New test.
	* testsuite/ld-powerpc/aix-tls-reloc.s: New test.
	* testsuite/ld-powerpc/aix-tls-section-32.d: New test.
	* testsuite/ld-powerpc/aix-tls-section-64.d: New test.
	* testsuite/ld-powerpc/aix-tls-section.ex: New test.
	* testsuite/ld-powerpc/aix-tls-section.s: New test.
include/
	* coff/internal.h (struct internal_aouthdr): Add new fields.
	* coff/rs6000.h (AOUTHDRÃ): Add new fields.
	* coff/rs6k64.h (struct external_filehdr): Likewise.
	* coff/xcoff.h (_TDATA), _TBSS): New defines
	(RS6K_AOUTHDR_TLS_LE, RS6K_AOUTHDR_RAS, RS6K_AOUTHDR_ALGNTDATA,
	RS6K_AOUTHDR_SHR_SYMTAB, RS6K_AOUTHDR_FORK_POLICY,
	RS6K_AOUTHDR_FORK_COR): New defines.
	(XMC_TU): Removed.
	(XMC_UL): New define.