Merge branch 'change_quit2' of http://ambre.pingoured.fr/cgit/subsurface

Pull patches to change behavior on exit from Pierre-Yves Chibon.

Pierry-Yves explains:
 "When someone opens a file, change something in it and try to quit, the
  program asked whether the data should be saved.

  If 'Ok' then it shows the save-window and the user can choose to save
  the file or rename it.

  My habits in such case would be that since I opened a specific file, I
  want to save to that specific file, therefore, when I press 'Ok', I
  want it to save automatically to the file I opened.

  So I have been working on changes that do:
   - When a file has been opened by the user, save to this same file if
     the user is 'Ok' while closing.
   - Add a 'Cancel' option to the pop-up window that offers to save the
     file while closing.
   - Add a 'Save As' entry in the file menu."

* 'change_quit2' of http://ambre.pingoured.fr/cgit/subsurface:
  Add a 'Save As' entry in the menu.
  Allow to cancel while trying to quit and the data was changed.
  When the file has been opened rely on it to save.