Delete GDI bitmap object before DC.

Dr. Memory complains about GDI misuse.
Log x264 bitrate and buffer size changes

Previously buffer size changes were not logged by the settings dialog
Show IDC_INFO only when necessary

Checking the video encoder should be sufficient, as long as noone adds
a audio encoding only mode
Fix NullVideoEncoder triggering IDC_INFO when changing bitrate/buffer
Abort stream if x264 opencl fails
MFT: remove unused async code and other cleanups.
Merge branch 'master' of https://github.com/jp9000/OBS into obsvce
Create IMFSample once and just add/remove buffers to/from it. Loop over ProcessInput and ProcessOutput in Encode.

Probably needs patched OBS::BufferVideoData.
Add filler NALs.
Modify OBS::ProcessFrame to be more compatible with MFT.