Return zero-fill packets when reading bitstreams
Return zero-fill packets when reading bitstreams

Zero-fill packets are required in certain conditions to create valid
bitstreams.  When reading a bitstream, make sure they are yielded and
printed.

Signed-off-by: Rick Altherr <8d1509bf509ebdf080240b52ca7c44886e3b1782@kc8apf.net>

SymbiFlow/prjxray,SymbiFlow/prjxray,SymbiFlow/prjxray,SymbiFlow/prjxray,SymbiFlow/prjxray