Properly set the unsigned/signed 8bit values

Hack to bypass GlowCtx initialization via GlowDraw when creating a context only to read some variables.

GTK: Small optimization: changed the redraw timer to a timeout, if the window has not been redrawn 40 ms after it was marked as dirty, then force a redraw.

QT: Chanegd the checkboxes to select mode In the PLC editor to radiobuttons, since only one should be activated at a time.

QT: Fixed double click. The second click is apparently not a second press event, but its own unique event.

GTK: Added a redraw timer, since GTK doesn't generate exposure/redraw events every 1 ms like QT does.