sourceLoc now much faster

changed a number of things:

1). in p2readsigfiles, changed the implementation so that it's similar
to p2Task(). Now it reads the sig portion of the source file.

2). for each frame, if sourceLoc is specified, we take the specified
region of src to do templateMatch(). This speeds up things by ~50x; a
comparison is about 10ms now instead of 0.7-1sec.