Remove the workaround for #11018 in two other places.

The bug is fixed, the workaround can be removed.

FFMPEG Plugin: Implement flushing of video frames from decoder.

- Video frames still contained in the video decoder are now flushed when there
are no encoded data chunks left (signaled by B_LAST_BUFFER_ERROR).
- New code was successfully tested with mpeg2_decoder_test. The last test image
is now decoded, too, resulting in a bump of the expected number of decoded
images.
- Refactor code to support flushing -and- keep the readability at a sane level.
- Remove some uncommented code for the sake of readability.
- Documentation updated accordingly.

MediaKit: Remove superflous code in mpeg2_decoder_test.

- Thanks to automatic video decoding parameter detection, we no longer need to
manually hack the correct parameters for this test to succeed, jiha!

Media Kit: Add workaround for #11018 to MPEG2 video stream decoder test.

The workaround triggers the loading of all media plugins prior to using
methods of class BMediaFormats. Using the function get_next_encoder()
is used because of two facts

1. It is publicly available and thus can be used by 3rd party apps,
too.
2. It is already available by including BMediaFormats.h, so there is
no need to include another header for this workaround.

Signed-off-by: Colin Günther <coling@gmx.de>
(cherry picked from commit 80354716fe8b25c81ec45bd96ae36e171228b8a0)

Media Kit: Add MPEG2 video stream decoder test.

- This test currently fails and thus showing that there is something wrong in
the Media Kit.
- This test was first developed and tested on Haiku R1 Alpha 4.1 where
every thing was hacked together to make this test succeed, thus showing that
the current Media Kit state of affair has some issues and not this test :)
- The test comes with documentation (@see mpeg2_decoder.test.cpp).

Signed-off-by: Colin Günther <coling@gmx.de>

Remove the workaround for #11018 in two other places.

The bug is fixed, the workaround can be removed.

FFMPEG Plugin: Implement flushing of video frames from decoder.

- Video frames still contained in the video decoder are now flushed when there
are no encoded data chunks left (signaled by B_LAST_BUFFER_ERROR).
- New code was successfully tested with mpeg2_decoder_test. The last test image
is now decoded, too, resulting in a bump of the expected number of decoded
images.
- Refactor code to support flushing -and- keep the readability at a sane level.
- Remove some uncommented code for the sake of readability.
- Documentation updated accordingly.

MediaKit: Remove superflous code in mpeg2_decoder_test.

- Thanks to automatic video decoding parameter detection, we no longer need to
manually hack the correct parameters for this test to succeed, jiha!

Media Kit: Add workaround for #11018 to MPEG2 video stream decoder test.

The workaround triggers the loading of all media plugins prior to using
methods of class BMediaFormats. Using the function get_next_encoder()
is used because of two facts

1. It is publicly available and thus can be used by 3rd party apps,
too.
2. It is already available by including BMediaFormats.h, so there is
no need to include another header for this workaround.

Signed-off-by: Colin Günther <coling@gmx.de>
(cherry picked from commit 80354716fe8b25c81ec45bd96ae36e171228b8a0)

Media Kit: Add MPEG2 video stream decoder test.

- This test currently fails and thus showing that there is something wrong in
the Media Kit.
- This test was first developed and tested on Haiku R1 Alpha 4.1 where
every thing was hacked together to make this test succeed, thus showing that
the current Media Kit state of affair has some issues and not this test :)
- The test comes with documentation (@see mpeg2_decoder.test.cpp).

Signed-off-by: Colin Günther <coling@gmx.de>