One way to avoid having a giant file having lots of lexer/grammar
definition is to spread them out to several interfaces.

To support this feature, need to add a @CookCCGrammar marker on the
interfaces.  Then the parser class that implements the interface should
have @CookCC marker (and CookCC would go check each interfaces).  With IDEA
or Eclipse, the overriding functions can be automatically generated.

One advantage of this approach allows sub-component of a language grammar
to be individually tested, by building separate parser classes that
implement selected interfaces.  The actual implementation of the language
can also be delayed, by simply using generated functions.