This commit adds 3 new properties to split output file in the output
`ffmpeg_muxer`.
- `max_time_sec` specifies the limit in seconds.
- `max_size_mb` specifies the limit in megabytes.
- `allow_overwrite` specifies to test an existing file.
If both `max_time_sec` and `max_size_mb` are not positive, the split
file feature won't be enabled.
Another output ffmpeg_mpegts_muxer shares the code but is not affected
since the output is used only for streaming.
Add and register an obs_output_info struct called
ffmpeg_hls_muxer. It uses ffmpeg's HLS muxer to stream output.
Add threading and buffer to reduce skipped frames.
Also add frame drop logic when there are too many packets in the
buffer for congestion control.
(Jim) Allows the ability to use stream keys with ffmpeg-mux -- this will
enable the ability to use it with certain services (such as YouTube)
which allow different protocols (such as HLS)
(Jim) Allows the ability to specify mux settings directly on the
output's structure itself rather than just via settings. This is useful
for network-based muxer outputs (such as HLS).
(Jim) printable_file allows the ability to keep a separate string for
logging which will not contain things like stream keys when used with
outputs such as HLS.
Norihiro Kamae
Maya Venkatraman