x86-64: Add some x32 ELF property tests

	* testsuite/ld-x86-64/property-x86-3-x32.d: New file.
	* testsuite/ld-x86-64/property-x86-4a-x32.d: Likewise.
	* testsuite/ld-x86-64/property-x86-4b-x32.d: Likewise.
	* testsuite/ld-x86-64/property-x86-3.d: Also pass
	-defsym __64_bit__=1 to asssembler.
	* testsuite/ld-x86-64/property-x86-4a.d: Likewise.
	* testsuite/ld-x86-64/property-x86-4b.d: Likewise.
	* testsuite/ld-x86-64/property-x86-3.s: Align to 4 bytes if
	__64_bit__ isn't defined.
	* testsuite/ld-x86-64/property-x86-4a.s: Likewise.
	* testsuite/ld-x86-64/property-x86-4b.s: Likewise.
	* testsuite/ld-x86-64/x86-64.exp: Run property-x86-3-x32,
	property-x86-4a-x32 and property-x86-4b-x32.