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.
Code submissions have continually suffered from formatting
inconsistencies that constantly have to be addressed. Using
clang-format simplifies this by making code formatting more consistent,
and allows automation of the code formatting so that maintainers can
focus more on the code itself instead of code formatting.
