Function() way of generating code breaks for slightly more complication %{...%} action snippets

(manual extract from #143)

* (SHA-1: 47206a3350d3359a8190c6ff342c42a17bc53d55) * patched the code generator as it broke on the offending line (where the action code is poured into a Function()) for action blocks such as this one:

    ... rule ...
    | TAN '(' e ')'
        {
            $$ = {
                token:      FKW_FUNCTION,
                token_attr: FKA_ABSOLUTE,
                childs:     [null, $3],
                loc_info:   @$,
                type:       FT_NUMBER,
                unit:       $3.unit,
                value:      Math.abs($3.value)
            };
        }

The object creation like that would produce a 'Unexpected symbol' error.