xtermExtendedUtf8Mouse
Indicate whether XTerm's UTF-8 extended mouse is enabled (mode 1005).
Normally, mouse events use three bytes for the flags, x, and y coordinate values. In UTF-8 mode, the number of bytes switches to be variable-length as the values are now UTF-8 encoded, and setting this property to true correctly changes the parser to consume the values as UTF-8.