x86: Merge X86_ISA_1_USED/X86_ISA_1_NEEDED properties

x86: Merge X86_ISA_1_USED/X86_ISA_1_NEEDED properties

If there are more than GNU property note in an input, we should merge
X86_ISA_1_USED and X86_ISA_1_NEEDED properties.

bfd/

	* elf32-i386.c (elf_i386_parse_gnu_properties): Merge
	GNU_PROPERTY_X86_ISA_1_USED and GNU_PROPERTY_X86_ISA_1_NEEDED
	properties.
	* elf64-x86-64.c (elf_x86_64_parse_gnu_properties): Likewise.

ld/

	* testsuite/ld-i386/i386.exp: Run property-x86-3.
	* testsuite/ld-x86-64/x86-64.exp: Likewise.
	* testsuite/ld-i386/property-x86-3.d: New file.
	* testsuite/ld-i386/property-x86-3.s: Likewise.
	* testsuite/ld-x86-64/property-x86-3.d: Likewise.
	* testsuite/ld-x86-64/property-x86-3.s: Likewise.