mpc-hc

Fix memory leak of CWnd (#107)

When seeking to a previous keyframe while video is playing, jump at least 500ms to avoid getting stuck on a frame. When paused it still goes to nearest keyframe.

Increase threshold for adding files to playlist from 500ms to 1s. This check triggers when the player is executed multiple times in very short period, e.g. due to selecting multiple files in Explorer.

Add comment about rare hang in filter graph builder

Also add VP9 profile 2 choice