liveHTTP: use calloc to ensure correct initiliazation of members

Sometimes, f_seglen ended up being garbage and resulted to a very long duration for the first segment in the m3u8 index file

Signed-off-by: Olivier Langlois olivier@trillion01.com
Acked-by: Ilkka Ollakka <ileoo@videolan.org>
Signed-off-by: Jean-Baptiste Kempf <jb@videolan.org>
Fingerprinter: fix formatting
liveHTTP: fix signedness warnings
RSS: add the "opacity" to the options list

Ref #7241