Misc about gold for aarch64 backend.

Misc about gold for aarch64 backend.

The patch does the following things:
  -- Add support for ifunc.
  -- Enable safe icf
  -- Add support for TLSLD relocations
     R_AARCH64_TLSLD_ADR_PAGE21,
     R_AARCH64_TLSLD_ADD_LO12_NC,
     R_AARCH64_TLSLD_MOVW_DTPREL_G1,
     R_AARCH64_TLSLD_MOVW_DTPREL_G0_NC.
     (R_AARCH64_TLSLD_MOVW_* are used by LLVM.)
  -- Add support for TLSLD->TLSLE relaxation.
  -- Add support for R_AARCH64_LD_PREL_LO19, R_AARCH64_ADR_PREL_LO21.
  -- Fix 2 encoding bugs in AArch64_relocate_functions::update_movnz.
  -- Correct TLS relocation properties in gold/aarch64-reloc.def.
  -- Update testsuite/icf_safe_so_test.cc, testsuite/icf_safe_test.sh.

gold/
2014-10-29  Han Shen  <shenhan@google.com>
            Jing Yu   <jingyu@google.com>

	* aarch64-reloc.def: Add LD_PREL_LO12, ADR_PREL_LO21,
	TLSLD_ADR_PAGE21, TLSLD_ADD_LO12_NC, TLSLD_MOVW_DTPREL_G1,
	TLSLD_MOVW_DTPREL_G0_NC. Change property of TLS relocations to
	Symbol::TLS_REF.
	* aarch64.cc (Target_aarch64::do_can_check_for_function_pointers): New
	method.
	(Target_aarch64::reloc_needs_plt_for_ifunc): New method.
	(Target_aarch64::tls_ld_to_le): New method.
	(Target_aarch64::aarch64_info): Enable can_icf_inline_merge_sections
	for 64bit targets.
	(Output_data_plt_aarch64::irelative_rel_): New data member.
	(Output_data_plt_aarch64::add_entry): Add irelative entries to plt.
	(Output_data_plt_aarch64::add_local_ifunc_entry): New method.
	(Output_data_plt_aarch64::add_relocation): New method.
	(Output_data_plt_aarch64::do_write): Add gold_assert on got_irelative
	offset. Add got_irelative size to got size.
	(AArch64_relocate_functions): Typedef AArch64_valtype. Replace long
	type string with the new typename.
	(AArch64_relocate_functions::update_adr): Replace parameter x with
	immed.
	(AArch64_relocate_functions::update_movnz): Correct wrong val mask.
	(AArch64_relocate_functions::reloc_common): New method.
	(AArch64_relocate_funcsions::rela_general): Extract common part out
	into reloc_common method.
	(AArch64_relocate_functions::rela_general): Likewise.
	(AArch64_relocate_functions::pcrela_general): Likewise.
	(AArch64_relocate_functions::adr): New method.
	(AArch64_relocate_functions::adrp): Calculate immed before calling
	update_adr.
	(AArch64_relocate_functions::adrp): Likewise.
	(AArch64_relocate_functions::movnz): Cast x to SignedW type when
	comparing x to 0. Calculate immed from ~x when x < 0.
	(Target_aarch64::optimize_tls_reloc): Add new cases for
	TLSLD_ADR_PAGE21, TLSLD_ADD_LO12_NC, TLSLD_MOVW_DTPREL_G1,
	TLSLD_MOVW_DTPREL_G0_NC.
	(Target_aarch64::possible_function_pointer_reloc): Implement this
	method.
	(Target_aarch64::Scan::local_reloc_may_be_function_pointer): Update
	comment.
	(Target_aarch64::Scan::local): Add codes to handle STT_GNU_IFUNC
	symbol. Add cases for TLSLD_ADR_PAGE21, TLSLD_ADD_LO12_NC,
	TLSLD_MOVW_DTPREL_G1, TLSLD_MOVW_DTPREL_G0_NC.
	(Target_aarch64::Scan::global): Add codes to handle STT_GNU_IFUNC
	symbol. Add cases for TLSLD_ADR_PAGE21, TLSLD_ADD_LO12_NC,
	TLSLD_MOVW_DTPREL_G1, TLSLD_MOVW_DTPREL_G0_NC.
	(Target_aarch64::make_plt_entry): Call add_entry with two more
	parameters.
	(Target_aarch64::make_local_ifunc_plt_entry): New method.
	(Target_aarch64::Relocate::relocate): Add cases for LD_PREL_LO19,
	ADR_PREL_LO21, TLSLD_ADR_PAGE21, TLSLD_ADD_LO12_NC,
	TLSLD_MOVW_DTPREL_G1, TLSLD_MOVW_DTPREL_G0_NC.
	(Target_aarch64::Relocate::relocate_tls): Add cases for
	TLSLD_ADR_PAGE21, TLSLD_ADD_LO12_NC, TLSLD_MOVW_DTPREL_G1,
	TLSLD_MOVW_DTPREL_G0_NC.
	* testsuite/icf_safe_so_test.cc: Correct test comment.
	* testsuite/icf_safe_test.sh: Add AArch64 arch.