Lexcat heuristics: PP false positives

[nschneid]

Ken Litkowski noticed that PP is erroneously the lexcat for in hope to, just about, and nothing but, which should be P. This is because the UPOS of the last word in the MWE is PART, ADV, or CCONJ. Under the current heuristics in lexcatter.py, an MWE is treated as P only if the last word is tagged as ADP or SCONJ.