This patch implements __get_cpuid_max() as an inline and __cpuid() and

__cpuid_count() as macros to be compatible with GCC's cpuid.h.  It also adds
bit_<foo> constants for the various feature bits as described in version 039
(May 2011) of Intel's SDM Volume 2 in the description of the CPUID
instruction.  The list of bit_<foo> constants is a bit exhaustive (GCC
doesn't do near this many).  More bits could be added from a newer version of
SDM if desired.

Patch by John Baldwin!

llvm-svn: 186696