emc/sai: dummy canon layer nullcanon.cc - for interpreter profiling

to cut out any canon overhead from profiling and timing, and measure
interpreter parsing speed only

to build the standalone interpreter (rs274) with dummycanon, do like so:

rm ../bin/rs274
make ../bin/rs274 USE_NULLCANON=1
SQ: preview module test case - no line numbers
SQ: previewmodule.cc - some basic stats