CPUID util add namespace if compiled as C++ Add comment about namespace for C++ Remove unnecessary includes
CPUID util add namespace if compiled as C++ Add comment about namespace for C++ Remove unnecessary includes

Bug: libyuv:858
Change-Id: I71473aff572752460a2f77b2b2058f78410b54af
Tested: g++ -Iinclude/ -o cpuid util/cpuid.c source/cpu_id.cc
Reviewed-on: https://chromium-review.googlesource.com/c/libyuv/libyuv/+/2163353
Reviewed-by: richard winterton <7813c392a2997235685e34a1ee2600a5031ac0a4@gmail.com>
Reviewed-by: Frank Barchard <52415189a3f67d375195cbbb6fdb1f1759498e57@chromium.org>
Commit-Queue: Frank Barchard <52415189a3f67d375195cbbb6fdb1f1759498e57@chromium.org>

lemenkov/libyuv,lemenkov/libyuv,lemenkov/libyuv,lemenkov/libyuv