Add configuration option to run the GC on exit

If "auto_gc" is enabled, the garbage collector for note files will be
run on every exit. As this is an experimental feature and may cause data
loss, this is disabled by default.

Signed-off-by: Lukas Fleischer <calcurse@cryptocrack.de>

src/calcurse.c

@@ -537,6 +537,8 @@ main (int argc, char **argv)
         case KEY_GENERIC_QUIT:
           if (conf.auto_save)
             io_save_cal (&conf, IO_SAVE_DISPLAY_BAR);
+          if (conf.auto_gc)
+            note_gc ();
 
           if (conf.confirm_quit)
             {