Add support for displaying and merging GNU_BUILD_NOTEs.

Add support for displaying and merging GNU_BUILD_NOTEs.

include	* elf/common.h (SHF_GNU_BUILD_NOTE): Define.
	(NT_GNU_PROPERTY_TYPE_0): Define.
	(NT_GNU_BUILD_ATTRIBUTE_OPEN): Define.
	(NT_GNU_BUILD_ATTRIBUTE_FUN): Define.
	(GNU_BUILD_ATTRIBUTE_TYPE_NUMERIC): Define.
	(GNU_BUILD_ATTRIBUTE_TYPE_STRING): Define.
	(GNU_BUILD_ATTRIBUTE_TYPE_BOOL_TRUE): Define.
	(GNU_BUILD_ATTRIBUTE_TYPE_BOOL_FALSE): Define.
	(GNU_BUILD_ATTRIBUTE_VERSION): Define.
	(GNU_BUILD_ATTRIBUTE_STACK_PROT): Define.
	(GNU_BUILD_ATTRIBUTE_RELRO): Define.
	(GNU_BUILD_ATTRIBUTE_STACK_SIZE): Define.
	(GNU_BUILD_ATTRIBUTE_TOOL): Define.
	(GNU_BUILD_ATTRIBUTE_ABI): Define.
	(GNU_BUILD_ATTRIBUTE_PIC): Define.
	(NOTE_GNU_PROPERTY_SECTION_NAME): Define.
	(GNU_BUILD_ATTRS_SECTION_NAME): Define.
	(GNU_PROPERTY_STACK_SIZE): Define.
	(GNU_PROPERTY_NO_COPY_ON_PROTECTED): Define.
	(GNU_PROPERTY_X86_ISA_1_USED): Define.
	(GNU_PROPERTY_X86_ISA_1_NEEDED): Define.
	(GNU_PROPERTY_X86_ISA_1_486): Define.
	(GNU_PROPERTY_X86_ISA_1_586): Define.
	(GNU_PROPERTY_X86_ISA_1_686): Define.
	(GNU_PROPERTY_X86_ISA_1_SSE): Define.
	(GNU_PROPERTY_X86_ISA_1_SSE2): Define.
	(GNU_PROPERTY_X86_ISA_1_SSE3): Define.
	(GNU_PROPERTY_X86_ISA_1_SSSE3): Define.
	(GNU_PROPERTY_X86_ISA_1_SSE4_1): Define.
	(GNU_PROPERTY_X86_ISA_1_SSE4_2): Define.
	(GNU_PROPERTY_X86_ISA_1_AVX): Define.
	(GNU_PROPERTY_X86_ISA_1_AVX2): Define.
	(GNU_PROPERTY_X86_ISA_1_AVX512F): Define.
	(GNU_PROPERTY_X86_ISA_1_AVX512CD): Define.
	(GNU_PROPERTY_X86_ISA_1_AVX512ER): Define.
	(GNU_PROPERTY_X86_ISA_1_AVX512PF): Define.
	(GNU_PROPERTY_X86_ISA_1_AVX512VL): Define.
	(GNU_PROPERTY_X86_ISA_1_AVX512DQ): Define.
	(GNU_PROPERTY_X86_ISA_1_AVX512BW): Define.

binutils* readelf.c (get_note_type): Add support for GNU_BUILD_NOTEs.
	(get_gnu_elf_note_type): Add support for GNU_PROPERTY_NOTEs.
	(decode_x86_isa): New function.
	(print_gnu_property_note): New function.
	(print_gnu_note): Handle GNU_PROPERTY_NOTEs.
	(print_gnu_build_attribute_description): New function.
	(print_gnu_build_attribute_name): New function.
	(process_note): Add support for GNU_BUILD_NOTEs.
	* objcopy.c (--merge-notes): New command line option.
	(copy_options): Add merge-notes.
	(copy_usage): Likewise.
	(is_merge_note_section): New function.
	(merge_gnu_build_notes): New function.
	(copy_object): Merge note sections if asked to do so.
	(skip_section): Add skip_copy parameter.  Add support for skipping
	merged note sections.
	(copy_relocations_in_section): Update call to skip_section.
	(copy_section): Likewise.
	(copy_main): Add support for merge-notes option.
	* doc/binutils.texi: Document the new option to objcopy.
	* NEWS: Mention the new feature.
	* testsuite/binutils-all/note-2-32.d: New test.  Checks note
	merging on 32-bit targets.
	* testsuite/binutils-all/note-2-32.s: New test source file.
	* testsuite/binutils-all/note-2-64.d: New test.  Like note-2-32.d
	but for 64-bit targets.
	* testsuite/binutils-all/note-2-64.s: New test source file.
	* testsuite/binutils-all/objcopy.exp: Run the new test.