Avoid linking with -lrt if not needed (e.g. recent GNU/libc),
simplify, and enable linking other library than libvlccore.

When not implicit, limits are mentioned in *_id description.

Useless then suspicious use in omxil.c might incur a regression.

Tries strongest match against decoder record

Like valgrind, the address sanitizer generates unusable leak reports if
plugins are unloaded.

Run 'make lcov' to produce the coverage report in the lcov/.
This requires lcov installed and the --enable-coverage configure flag.

fixes #14399

When p_block was NULL, DecoderThread was draining its packetizer or its
decoder, but was not draining both (when a packetizer was used).

In order to avoid flickering on local content