Now includes mouse support. A mouse click on an item in the menu will make it...

Now includes mouse support.  A mouse click on an item in the menu will make it the currently highlighted item, and if the scrollbar is enabled, clicking above/below the solid scroll block will do a page up/down.
I'm wondering if there's a function (other than time()) that has higher resolution than 1 second (perhaps milliseconds?) so I can detect a double-click in a short amount of time (to perhaps add an item when multi-select is enabled).
I also saw the 'motion' variable, and I'm wondering if that coudl be used to detect mouse motion when the button is pressed (so that the menu can scroll when the mouse is moved while the mouse button is pressed over the scroll block).