[winswitch] Centos libvpx.so.4 dependency

[Bob Tennent]

On Centos 7:

Resolving Dependencies
--> Running transaction check
---> Package PyOpenGL.noarch 0:3.1.1a1r1-1.el7_2 will be obsoleted
---> Package PyOpenGL-accelerate.x86_64 0:3.1.1a1r1-1.el7_2 will be obsoleted
---> Package ffmpeg-xpra.x86_64 0:3.0.2-1.el7_2 will be updated
---> Package ffmpeg-xpra.x86_64 0:3.1.2-1.el7_2 will be an update
--> Processing Dependency: libvpx.so.4()(64bit) for package: ffmpeg-xpra-3.1.2-1.el7_2.x86_64

On Centos 6:

Resolving Dependencies
--> Running transaction check
---> Package ffmpeg-xpra.i686 0:3.0.2-1.el6_8 will be updated
---> Package ffmpeg-xpra.i686 0:3.1.2-1.el6_8 will be an update
--> Processing Dependency: libvpx.so.4 for package: ffmpeg-xpra-3.1.2-1.el6_8.i686