libyuv updates for better code generation on OSX clang for scale BUG=478 TEST=build libyuv and disassemble scale.o with otool -tV.  Should use registers for C loops, not stack. Review URL: https://webrtc-codereview.appspot.com/550005
libyuv updates for better code generation on OSX clang for scale
BUG=478
TEST=build libyuv and disassemble scale.o with otool -tV.  Should use registers for C loops, not stack.
Review URL: https://webrtc-codereview.appspot.com/550005

git-svn-id: 917f5d3ca488f358c4d40eaec14422cf392ccec9@2155 4adac7df-926f-26a2-2b94-8c16560cd09d

mwgoldsmith/libilbc,ShiftMediaProject/libilbc,ShiftMediaProject/libilbc,ShiftMediaProject/libilbc,TimothyGu/libilbc,TimothyGu/libilbc,mwgoldsmith/ilbc,mwgoldsmith/libilbc,mwgoldsmith/ilbc,TimothyGu/libilbc,mwgoldsmith/libilbc,mwgoldsmith/libilbc,mwgoldsmith/ilbc,ShiftMediaProject/libilbc,TimothyGu/libilbc,TimothyGu/libilbc,ShiftMediaProject/libilbc,mwgoldsmith/ilbc