elfedit: Add --enable-x86-feature/--disable-x86-feature

elfedit: Add --enable-x86-feature/--disable-x86-feature

Add --enable-x86-feature and --disable-x86-feature options to elfedit
to set and clear the IBT and SHSTK bits in program property in ELF
executables and shared objects.

binutils/

	* doc/binutils.texi: Document --enable-x86-feature and
	--disable-x86-feature options for elfedit.
	* elfedit.c: Include "config.h" and <sys/mman.h>.
	(enable_x86_features): New.
	(disable_x86_features): Likewise.
	(update_gnu_property): Likewise.
	(elf_x86_feature): Likewise.
	(process_file): Call update_gnu_property on ET_EXEC or ET_DYN
	file.
	(command_line_switch): Add OPTION_ENABLE_X86_FEATURE and
	OPTION_DISABLE_X86_FEATURE.
	(options): Add--enable-x86-feature and --disable-x86-feature.
	(usage): Likewise.
	(main): Handle OPTION_ENABLE_X86_FEATURE and
	OPTION_DISABLE_X86_FEATURE.

ld/

	* testsuite/config/default.exp (ELFEDIT): New.
	* testsuite/ld-elf/linux-x86.exp (elfedit_test): New proc.
	Run elfedit tests.
	* testsuite/ld-elf/x86-feature-1a.rd: New file.
	* testsuite/ld-elf/x86-feature-1b.rd: Likewise.
	* testsuite/ld-elf/x86-feature-1c.rd: Likewise.
	* testsuite/ld-elf/x86-feature-1d.rd: Likewise.
	* testsuite/ld-elf/x86-feature-1e.rd: Likewise.