Should close #3536

Close #3944

https://bugs.gentoo.org/show_bug.cgi?id=333723

 * fetch the list of video for one item only if required
 * use the provided thumbnail if available.

There still are some formatting issues (e.g. --cdda-track)

This reverts commit 10d0f724.

add needed header to fix build
process all config items
process all items of config lists (off by one)
fix display of lists: some option have a space in their name

It allows to:
 - properly support filters that do not have 1:1 input/output relation
 (yadif2x, bob, ... are back).
 - filter only once each picture (for the 'static' filter chain). It
 fixes filters with state behavior.
 - display as soon as possible the first frame after a flush.

There are still a few issues:
 - when paused, on filter changes, the picture displayed step forward the
 first time.
 - preventive frame dropping is not enough agressive.

 Due to the way dynamic configuration is managed, the static chain contains
only deinterlace/postproc for now.

As reported by xxcv

Close #3996

Should fix #4078 , same issue was in linux side also.

 I am not sure it had consequences, but it seems more logical and
it follows the libxml2 code example I found (reader1.c).

 xml_ReaderReset(reader, NULL) followed by xml_ReaderDelete(reader) lead
to a double free.
 xml_ReaderReset(reader, stream) would leak the module upon error.