This gives a similar structure to libwebp and fixes a bug where passing
NULL to SharpYuvInit() would unconditionally set optimized function
pointers. SharpYuvInit() is left as an undocumented public function and
SharpYuvGetCPUInfo is kept private to serialize updates to the pointer.
Change-Id: Id72fbf3ba5b396367510e3bcd1ee2e4e11b95b8c
It's self contained apart from a dependency on src/webp/types.h and src/dsp/cpu.h
For now it's only set up as an internal library, not an installable one.
Webp doesn't depend on it yet, the code is only duplicated.
Change-Id: I752799894f9d4105d0d296ddebd9f9641181a1ec
