Fix compilation error with Bison >=2.6

Because of the way newer Bison versions arrange the prototypes in the
generated header files, there will be a compiler error because of
inconsistent prototypes if YYPARSE_PARAM is used.  Moreover, Bison 3.0
removes support for YYPARSE_PARAM altogether.  Use the declaration
%parse-param instead.
Merge pull request #4 from petere/yyparse-param-fix

Fix compilation error with Bison >=2.6