mpgaf: fix various parsing mistakes
rtpd: fix warning
ts_psig: limit PAT/PMT versions to 5 bits
ts_mux: add the ability to avoid memleak

Memleak which can happen if one of the inputs doesn't deliver any packet
when it is supposed to (video and audio inputs). Use upipe_sink_set_max_length
to limit the number of buffered packets per input.
use standard functions for set/get_option
new filter decode pipe

This wraps around avcodec_decode to make sure a new pipe is created if the
flow def is changed and avcdec refuses a set_flow_def.