x86-64: Use long NOPs for Intel Core processors

x86-64: Use long NOPs for Intel Core processors

Use long NOPs for Intel Core processors since they are faster than
multiple NOPs.  Don't use them for 64-bit processors by default since
Intel Atom processors can only decode 4 prefixes in 1 cycle.

	* config/tc-i386.c (alt64_9): New.
	(alt64_10): Likewise.
	(alt64_11): Likewise.
	(alt64_12): Likewise.
	(alt64_13): Likewise.
	(alt64_14): Likewise.
	(alt64_15): Likewise.
	(alt64_patt): Likewise.
	(i386_generate_nops): Use alt64_patt for Intel Core processors
	in 64-bit mode.
	* testsuite/gas/i386/x86-64-nops-1-core2.d: Expect long NOPs.
	* testsuite/gas/i386/x86-64-nops-4-core2.d: Likewise.
	* testsuite/gas/i386/ilp32/x86-64-nops-1-core2.d: Replace
	../x86-64-nops-1.d with ../x86-64-nops-1-core2.d.
	* testsuite/gas/i386/ilp32/x86-64-nops-4-core2.d: Replace
	../x86-64-nops-4.d with ../x86-64-nops-4-core2.d.