And remove setup thread callbacks init since it's not supported anymore.

Signed-off-by: Jean-Baptiste Kempf <jb@videolan.org>

In particular, move \file stanzas inside groups.

This confused Doxygen and hid hypothetically invalid casts.

If a portable/ folder is next to the libvlccore.dll binary, it will use
it for most configuration and other files.

Close #9751, #2114 and #12679
Signed-off-by: Jean-Baptiste Kempf <jb@videolan.org>

problem reported by Timothy B. Terriberry" <tterribe@xiph.org>

fmt cat is checked/mapped earlier against handler

Close #14803

Also adds the missing restart on MP4Leaf demux mode

8 and a half years should have been enough to transition.