softhdcuvid/softhdvaapi/softhddrm with hevc and UHD

@lnj Regarding crashes: It is the same as with the last kernel. It crashes after 5-10 exits. In the following case it was after the 6th exit.

@jojo61 :
(Code, 20 lines)

@cinfo War das mpv mit Debug infos gebaut, (aber da spricht der Laie aus mir)