MFV r302423:
Bring older verbatim version of cpuid.h

This file is used regularly in FreeBSD builds but we usually use the
similar file provided by clang.

By providing the older file introduced in GCC 4.3, we hope to mimic
better what is provided by an external toolchain.

Obtained from: GCC-4_3-branch (SVN rev. 129548, pre GPLv3)