code: function unicodeEscape (warns, line, t) { // [], int, str
  	var hex = t.substring(2);
  	if (hex == '') return null;
  	if (!validHex(hex)) {
  		warnl(warns, line, "\"" + t + "\": invalid hex code.");
  		return "";
  	}
  	return String.fromCharCode(parseInt(hex, 16))
  }
docs: generate a warning if we are keeping them; prints it out if we were asked to handle a Wylie unicode escape, \\uxxxx or \\Uxxxxxxxx