h264: don't initialize missing pictures when using VDPAU.

This fixes an assertion failure when running mplayer -vc ffh264vdpau.

Reported by irc user ioni.
lavfi/noise: switch to AVLFG noise generator

Signed-off-by: Paul B Mahol <onemda@gmail.com>
v4l2: try to fix build on BSD

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>