tests: add overlay rgb and yuv444 tests

Also rename overlay test to overlay_yuv420 accordingly.
lavu/opt-test: do not explicitly set default value in test_ctx

Let av_opt_set_defaults() set the value, which is simpler and more
idiomatic.
lavu/opt: fix weird align
Revert "lavf/concatdec: define "ffcat" and "ffconcat" extensions"

This reverts commit 6cc12353a88dfb21c4c5a38e6c83280483b0ec88.

Conflicts:
	libavformat/version.h

Allowing to automatically select the concat demuxer raises
security concerns, as it allows a possibly hostile file to
access any file on the system. Guessing the format based on
the file name extension does not allow to enable the safe
mode designed to avoid it.
doc/muxers: specify that tee needs -map.

Address trac ticket #2311.
lavu/eval: add native support to lte and lt functions
examples/muxing: fix memory leak.

Do not re-call avcodec_get_context_defaults3(), it is already
called by avformat_new_stream() and it leaks the codec
priv_data that was already allocated.

Use avformat_free_context() instead of freeing (not)
everything manually.

Fix trac ticket #2322.
lavf/concat: compute duration if possible.
lavfi: port MP stereo3d filter

Signed-off-by: Paul B Mahol <onemda@gmail.com>
lavfi/mp: drop mp=stereo3d filter

The filter has been natively integrated into libavfilter.

Signed-off-by: Paul B Mahol <onemda@gmail.com>
lavfi/overlay: add support for partial overlaying

Partially rework the iteration logic, in order to limit iteration only
for the clipped overlay region.
lavfi/overlay: improve log message warning in case of clipped overlay
doc/showspectrum: add some examples.
doc/filters: make examples a bit more consistent.

Create dedicated subsection and itemize. Not done for every filters, but
a large part is done.
lavfi/deshake: support named options.
vf_stereo3d: Add AVOption table terminator

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
asfdec: dont truncate type 2-5 values

Fixes use of uninitialized variables and possible out of array accesses

Found-by: Mateusz "j00ru" Jurczyk and Gynvael Coldwind
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>