httpclient: Deal with "206 Partial Content" when we didn't ask for it.

Some servers, when reusing a HTTP connection, may return "206 Partial Content"
if a previous request was a range request but the new one isn't.
hls: Avoid calling sub_scanner repeatedly if nothing will be scanned by it
rpi: If video duration is unknown, estimate it based on PTS

Fixes #1821
RTMP: Set media source info

Fixes #1822
rpi: Show video frame resolution in media info

Fixes #1823
HLS: More robust handling of corrupted segments
rpi: Include 'linux_process_monitor' in build

Fixes #1825
rpi/cec: Always require Stop x 2 to Stop when using Stop as alt-key

Also map Stop + Dpad to move operations
ps3: Nag a bit more about donations if it's never turned on by the user