lavf: make av_set_pts_info private.

libavdevice/alsa-audio-dec.c

libavdevice/bktr.c

libavdevice/fbdev.c

libavdevice/jack_audio.c

libavdevice/libcdio.c

libavdevice/libdc1394.c

libavdevice/oss_audio.c

libavdevice/pulse.c

libavdevice/sndio_dec.c

libavdevice/v4l.c

libavdevice/v4l2.c

libavdevice/vfwcap.c

libavdevice/x11grab.c

libavformat/4xm.c

libavformat/aacdec.c

libavformat/adxdec.c

libavformat/aiffdec.c

libavformat/aiffenc.c

libavformat/amr.c

libavformat/anm.c