Support 64-bit entry size in SHT_HASH (for s390).

Support 64-bit entry size in SHT_HASH (for s390).

gold/
	* dynobj.cc (Dynobj::create_elf_hash_table): Create hash table with
	target-specific entry size.
	(Dynobj::sized_create_elf_hash_table): Add size template parameter.
	* dynobj.h (Dynobj::sized_create_elf_hash_table): Likewise.
	* layout.cc (Layout::create_dynamic_symtab): Set entsize to
	hash_entry_size.
	* target.h (Target::hash_entry_size): New method.
	(Target::Target_info::hash_entry_size): New data member.

	* aarch64.cc (Target_aarch64::aarch64_info): Add hash_entry_size.
	* arm.cc (Target_arm::arm_info): Likewise.
	(Target_arm_nacl::arm_nacl_info): Likewise.
	* i386.cc (Target_i386::i386_info): Likewise.
	(Target_i386_nacl::i386_nacl_info): Likewise.
	(Target_iamcu::iamcu_info): Likewise.
	* mips.cc (Target_mips::mips_info): Likewise.
	(Target_mips_nacl::mips_nacl_info): Likewise.
	* powerpc.cc (Target_powerpc::powerpc_info): Likewise.
	* sparc.cc (Target_sparc::sparc_info): Likewise.
	* tilegx.cc (Target_tilegx::tilegx_info): Likewise.
	* x86_64.cc (Target_x86_64::x86_64_info): Likewise.
	(Target_x86_64_nacl::x86_64_nacl_info): Likewise.
	* testsuite/testfile.cc (Target_test::test_target_info): Likewise.