cleanup yuv for consistency.  stride, return int, negative heights, inplace conversions, lower case names, filter enum, uint, planarfunction updates, remove common.h, remove common/ folder, cpuid header public, move headers into libyuv/, add libyuv.h, fixed header guards, remove internal timing from scale, tweaks for llvm build, videocommon simplified
BUG=none
TEST=Talk builds on all platforms against libyuv.
Review URL: http://webrtc-codereview.appspot.com/226003

git-svn-id: http://libyuv.googlecode.com/svn/trunk@31 16f28f9a-4ce2-e073-06de-1de4eb20be90