Fixed bug in kdesk, ScreenSaverFinish hooks not being called

 * The signal *ignore* mode was set before starting the screen saver,
   consequentely its return code was -1, and the icon hooks were not
   being started for the ScreenSaverFinish case.

 * Added missing explicit libraries in the makefile related to X11 APIs,
   this was probably caused by the reorganization of the libkdesk-dev package.