FIX to Contextual Pattern Matching

Level: Small

The descriptions in Sections 3.1 and 3.2 do not consider that the DLCP grammar is of a more general type, a run-length CFG. Nevertheless, this can be handled and the descriptions can be greatly simplified by using as black boxes some operations described in [12]. Further, within the space we use we can reduce the O(m log log n) time to O(m). A version with those fixes has been arxived.