Drawing a Button
GUI_BTN text$, x1%, y1%, x2%, y2% [, obj%=-1]
This procedure draws a button from (x1,y1) to (x2,y2) with the caption text.
The button can be queried by GUI_QBTN!.
If obj is >0, the element is registered in the AutoTouch table and can be queried by GUI_TOUCH.