ConfigEditorPopup
On creating the popup, config values were always read and used. Do this if the
application does not provide its own variables. The values are still committed
to the config file in the usual way (on control destruction). The application
may restore them to its own variables during setup.
- perform scanning in a thread
- change the label of the scan button
- trigger cancel with the same button and with the ESC key
- process all GUI updates in asynchronous mode.
Do not use a top window as parent of popups:
- If a top window goes away in an application with multiple instances of
XInsaneWidget, any call to a scanner widget leads to a crash.
Minor changes.