Disable Libav's AVX and FMA4 optimizations under Windows x86_64.

They cause crashes in avresample.

SSE* optimizations are still enabled, so the performance hit should be pretty minimal.



git-svn-id: svn://svn.handbrake.fr/HandBrake/trunk@5409 b64f7644-9d1e-0410-96f1-a4d463321fa5