Convert XGETBV to equivalent byte form in GetXCR0Eax (#69)
Convert XGETBV to equivalent byte form in GetXCR0Eax (#69)

osxcross (https://github.com/tpoechtrager/osxcross) gives the following error, which also happens with regular gcc on OS X (https://github.com/asmjit/asmjit/issues/78):
```
cpu_features/src/cpuinfo_x86.c:44:no such instruction: `XGETBV'
```
google/cpu_features,google/cpu_features,google/cpu_features