1. Minor improvements and fixes to checkboxes. It is now possible to define actions just like for other buttons (in which case the control variable in the FUNC parameter will be updated AND the action will be performed.)
Also, since the action flag for a command line action is zero, unless you specify a conflicting flag, the assumption is that the CMD parameter contains a command line to execute. If you only want the control variable updated and don't want a command line action, make sure to set the FUNC parameter to NULL (or "").
