fixes to compile on OS X (tested 10.8.5)

Confirms that mid-2013 MacBook Airs have support for RTM and HLE.

Note: also requires updating /usr/lib/clang/4.2/include/cpuid.h to latest version available here: https://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Headers/cpuid.h?view=co