Revert "Partial update of MozillaBuild make files."

This reverts commit 11563cb3850ba001e3fbe838599e1509f043a79c.
Always build libvpx encoder files regardless of --disable-webrtc
Part 1: Update libvpx build files (x86)
Merge pull request #3 from binoc-software/BINOC_OUTBOUND

Merge contributed libvpx 1.3.0 commits from BinOC