Re-remove #include "tokens.h" to permit reusing lexer between parsers.

Note: the proper token definition is fed in by the make rules
explicitly using "clang -include".
Update divergent token sets between tokens.h and parser grammars.
Fix printf warning.
Fix LDFLAGS so lexer links (needs -lm for pow()).
Merge pull request #7 from ptgreen/build-fixes

Build fixes