- clean up the code a bit (with a large trout)
- take care of buttons : 
  + variable button width (know font size)
  + abbreviate buttons names if buttons bar is too large
  + add left & right arrows if buttons bar is too large
- release windows during exits (use save set ?)
- check that new hints engine works with several
  conflicting hints
- look at XWMHints struct for keyboard input hints
- add config file support
- optionnaly restore original window size for released windows
- add automake support
