refactored ccnl-ext-nfnkrivine.c which had grown too large and hard to read:
- ZAM instructions and builtin operations are separated (new file ccnl-ext-nfnops.c)
- new ZAM_nextToken() for parsing the expression, prepares for binary encoding of term or introduction of hash tables for faster lookup
- ZAM_nextToken() also searches for builtin operations