Fix PiP when using OpenGL output

Viewport must be of the output window, not of the main video currently playing
Fix incorrect deletion of allocated buffers.

Under some circumstances, delete was using instead of delete[]. Allocate buffer with ffmpeg av_malloc to have them 16/32-bytes aligned
Allocate VideoFrame buffer using av_malloc, and mythframe utility routines.

Will need to have memory aligned frame in a future commit
Uses 16-bytes aligned memory buffer.

This allows FFmpeg to use SSE accelerated code
Add support for frames where pitch > width

This allows to create frames where all lines are 16-bytes aligned, allowing for more efficient SSE acceleration.
Add frame conversion and copy utility routines, to simplify the code
Create pitch/strides that are a multiple of 32 bytes

Allows all lines in a frame to be 16-bytes aligned
Fix PiP with VDPAU on mesa's drivers

This is due to a bug in mesa's vdpau implementation.
https://bugs.freedesktop.org/show_bug.cgi?id=80561

So as a work around, create a dummy bitmap surface and use this.
Limit the work around to non-nvidia drivers

There is still a remaining issue, only one PiP shows at a time. This is due to another bug in mesa's vdpau VdpVideoMixerRender, it clears the whole destination surface. So you only see the last PiP window.
Properly handle when libmythbluray is unable to open a bluray, should libaacs or libbd+ failed to decrypt.

It would otherwise leave the BD drive in an unmounted state, and sometimes a crash when attempting to read from the drive
Merge branch 'devel/opengl'