RSS: fix opacity management

Close #7241
RSS: small cosmetics change
filter_chain: fix potential undefined behavior

If p_chain->first is NULL, we should not take the address of first->filter.
vdpau: fix redundant const qualifier

Was meant as constant pointer and constant pointed data.
es_out: fix potential division by zero
TS mux: start timestamps from 0

Make mplayer timeline display nicer
Merge remote-tracking branch 'vlc/master' into native-libde265-codec

Merge vlc ts.c