nal: concatenate and escape row data while building row-start array for header

This way we only need to do a single pass over each slice NAL looking for start
code emulations; and there is one less memcopy. countStartCodeEmulations() and
appendSubstream() methods could be removed.
move lfcuParam to local
move m_bEdgeFilter to local
cleanup unused TComLoopFilter::loopFilterPic
writer: nits