RISC-V: Support ELF attribute for gas and readelf.

RISC-V: Support ELF attribute for gas and readelf.

	2019-01-16  Kito Cheng  <kito@andestech.com>
		    Nelson Chu  <nelson@andestech.com>

	bfd/
	* elfnn-riscv.c (riscv_elf_obj_attrs_arg_type): New.
	(elf_backend_obj_attrs_vendor): Define.
	(elf_backend_obj_attrs_section_type): Likewise.
	(elf_backend_obj_attrs_section): Likewise.
	(elf_backend_obj_attrs_arg_type): Define as
	riscv_elf_obj_attrs_arg_type.
	* elfxx-riscv.c (riscv_estimate_digit): New.
	(riscv_estimate_arch_strlen1): Likewise.
	(riscv_estimate_arch_strlen): Likewise.
	(riscv_arch_str1): Likewise.
	(riscv_arch_str): Likewise.
	* elfxx-riscv.h (riscv_arch_str): Declare.
	binutils/
	* readelf.c (get_riscv_section_type_name): New function.
	(get_section_type_name): Add handler for RISC-V.
	(riscv_attr_tag_t): Declare.
	(riscv_attr_tag): New.
	(display_riscv_attribute): New function.
	(process_attributes): Add handler for RISC-V.
	* testsuite/binutils-all/strip-3.d: Remove .riscv.attribute
	section.
	gas/
	* config/tc-riscv.c (DEFAULT_RISCV_ATTR): Define to 0 if not defined.
	(riscv_set_options): Add `arch_attr` field.
	(riscv_opts): Set default value for arch_attr.
	(riscv_write_out_arch_attr): New.
	(riscv_set_public_attributes): Likewise.
	(riscv_md_end): Likewise.
	(riscv_convert_symbolic_attribute): Likewise.
	(s_riscv_attribute): Likewise.
	(explicit_arch_attr): Likewise.
	(riscv_pseudo_table): Add .attribute to the table.
	(options): Add OPTION_ARCH_ATTR and OPTION_NO_ARCH_ATTR
	enumeration constants.
	(md_longopts): Add `march-attr' and `mno-arch-attr' options.
	(md_parse_option): Handle the new options.
	(md_show_usage): Document the `march-attr' option.
	* config/tc-riscv.h (md_end): Define as riscv_md_end
	(riscv_md_end): Declare.
	(CONVERT_SYMBOLIC_ATTRIBUTE): Define as
	riscv_convert_symbolic_attribute.
	(riscv_convert_symbolic_attribute): Declare.
	(start_assemble): Declare.
	* testsuite/gas/elf/elf.exp: Adjust test case for section2.e.
	* testsuite/gas/elf/section2.e-riscv: New.
	* testsuite/gas/riscv/attribute-01.d: New test
	* testsuite/gas/riscv/attribute-02.d: Likewise.
	* testsuite/gas/riscv/attribute-03.d: Likewise.
	* testsuite/gas/riscv/attribute-04.d: Likewise.
	* testsuite/gas/riscv/attribute-04.s: Likewise.
	* testsuite/gas/riscv/attribute-05.d: Likewise.
	* testsuite/gas/riscv/attribute-05.s: Likewise.
	* testsuite/gas/riscv/attribute-06.d: Likewise.
	* testsuite/gas/riscv/attribute-06.s: Likewise.
	* testsuite/gas/riscv/attribute-07.d: Likewise.
	* testsuite/gas/riscv/attribute-07.s: Likewise.
	* testsuite/gas/riscv/attribute-08.d: Likewise.
	* testsuite/gas/riscv/attribute-08.s: Likewise.
	* testsuite/gas/riscv/attribute-unknown.d: Likewise.
	* testsuite/gas/riscv/attribute-unknown.s: Likewise.
	* testsuite/gas/riscv/empty.l: Likewise.
	* doc/c-riscv.texi (.attribute): Add documentation.
	* configure.ac (--enable-default-riscv-attribute): New options.
	* configure: Re-generate.
	* config.in: Re-generate.
	include/
	* elf/riscv.h (SHT_RISCV_ATTRIBUTES): Define.
	(Tag_RISCV_arch): Likewise.
	(Tag_RISCV_priv_spec): Likewise.
	(Tag_RISCV_priv_spec_minor): Likewise.
	(Tag_RISCV_priv_spec_revision): Likewise.
	(Tag_RISCV_unaligned_access): Likewise.
	(Tag_RISCV_stack_align): Likewise.