[Cin] little patch for ffmpeg 5.1 plugins

[Andrea paz]

For plugins.txt:

overlay: blend a source audio track in a target audio track
Compressor_multi: compressor that acts on 3 distinct frequency bands
instead of the entire single spectrum.

PGS doesn't work in CinGG so it has to be removed. I don't understand
because I got it into plugins.txt. Sorry.

For plugin.opts:

F_blackdetect is a typo; The right name is F_blockdetect. Sorry.
Another typo is F_asoectralstats instead of F_aspectralstats.

Other errors:

1080 to 480: No, it is correct. The interlaced semi-field of the
source is 540; then the plugin converts it to 480 which is the result
wanted.