[GAS][AARCH64]Add TLSDESC large memory model support.

[GAS][AARCH64]Add TLSDESC large memory model support.

bfd/

2015-10-02  Renlin Li <renlin.li@arm.com>

	* elfnn-aarch64.c (elfNN_aarch64_howto_table): Check overflow for
	BFD_RELOC_AARCH64_TLSDESC_OFF_G1.

gas/

2015-10-02  Renlin Li <renlin.li@arm.com>

	* config/tc-aarch64.c (s_tlsdescadd): New.
	(s_tlsdescldr): New.
	(md_pseudo_table): Handle tlsdescadd and tlsdescldr pseudo ops.
	(reloc_table): Add entries for BFD_RELOC_AARCH64_TLSDESC_OFF_G0_NC and
	BFD_RELOC_AARCH64_TLSDESC_OFF_G0_NC.
	(process_movw_reloc_info): Support AARCH64_TLSDESC_OFF_G1 and
	    AARCH64_TLSDESC_OFF_G0_NC.
	(md_apply_fix): Likewise.
	(aarch64_force_relocation): Likewise.

gas/testsuite/

2015-10-02  Renlin Li <renlin.li@arm.com>

	* gas/aarch64/reloc-tlsdesc_off_g0_nc.d: New.
	* gas/aarch64/reloc-tlsdesc_off_g0_nc.s: New.
	* gas/aarch64/reloc-tlsdesc_off_g1.d: New.
	* gas/aarch64/reloc-tlsdesc_off_g1.s: New.
	* gas/aarch64/tls-desc.d: New.
	* gas/aarch64/tls-desc.s: New.