code: function regexes_for_category(lexer, category) {
    var REs = [];
    var done = false;
    for(var i = 0; !done && i < lexer.dialects.length; i++) {
      var dialect = lexer.dialects[i];
      if(dialect.lextab) {
        var categoryentry = dialect.lextab.find(function(lextabentry) {
           return lextabentry.category == category;
        });
        if(categoryentry) {
          REs.push(categoryentry.match);
  
          // if they've set entry.replace=true this dialect's
          // entry replaces other dialects' entries:
          done = categoryentry.replace;
        }
      }
    }
    return REs;
  }
docs: utility function accumulates all the regular expressions
  for a given token category and returns them in an array