* FFmpeg4 support. Compile warnings fixes. Credit goes to many people, including ferdnyc, peterM, and other awesome folks!
* Adding environment checking to enable/disable omp taskwait after each video/audio frame is processed. This is experimental for some users with crashes.
* Moving `omp taskwait` to after the ProcessVideoPacket() method, since that is the only place it is useful.
* Fixing crashes on missing Clip source file, and changing FFmpeg scaling algorthm from SWS_BILINEAR to SWS_LANCZOS (for higher quality scaling)
* Update FindFFmpeg.cmake module, and updating build script. Also enabling debug builds.
* Updating experimental travis build script
* Fixed unit test for newer version of FFmpeg (audio resampling)
* Experimental travis multiple jobs
* Adding OMP schedule hint (thanks PeterM), which prevents crashes in some circumstances.
Only tested on Linux though due to absense of hardware/software.
Tested to compile on Ubuntu 14.04, 16.04, 18.04, and 18.10
Acceleration only available on systems with ffmpeg 3.2 and up
Very early code, work in progress.
Issues to be fixed soon:
if hardware cannot decode because the size is too big it keeps trying.
more interfaces supported like vdpau in Linux
error handling
user interface
Many commented lines of code are still in the source to help people start
who may want to help.
decoding HW_DE_DEVICE_SET and/or encoding HW_EN_DEVICE_SET
Possible options are /dev/dri/renderD128 for the first,
/dev/dri/renderD129 for the second, and so on.
* Adding strict experimental to FFmpegReader and Writer (hopefully allowing all the encoders to be used)
(cherry picked from commit 1bcd1e5)
* init all formats and codecs before checking if valid
(cherry picked from commit 7250226)
