[Discuss-gnuradio] depad for atsc 2

[Charles Swiger]

I just added atsc_depad to cvs gr-atsc.

The 2.x code worked thru derandomizer, but the output was
atsc_mpeg_packet padded out to 256, which xine/mplayer won't
play. Kludging atsc_mpeg_packet pad to 0 in atsc_types.h 
worked with a warning from gnuradio about output not being
a power-of-2.  atsc_depad reads padded atsc_mpeg_packets
and writes 188 byte char packets. That function might be
better built into derandomizer anyway.

Also put the 0.9 boundary checking in the atsc_viterbi_decoder.
That was causing problems getting past bumps in the input
signal like usrp overrun dropped packets.

Also added the missing gr_agc.h for atsc_fpll.

--Chuck