Add CC clobber to cpuid call

This should not be needed, but it does not hurt. According to Ian Lance Taylor (http://gcc.gnu.org/ml/gcc-help/2014-02/msg00023.html), the CC clobber causes GCC to forget its internal representation of flag state. It should not be needed for cpuid. However, Clang has some odd behave in a couple of versions of its compiler when using cpuid. Both JW and UB experienced it on separate occassions.

cpu.cpp

@@ -113,6 +113,7 @@ bool CpuId(word32 input, word32 output[4])
 # endif
 			: "=a" (output[0]), "=D" (output[1]), "=c" (output[2]), "=d" (output[3])
 			: "a" (input), "c" (0)
+			: "cc"
 		);
 	}