Amends the following compiler warnings:

 ```
 Screen.c: In function ‘nxagentReconnectScreen’:
 Screen.c:3547:7: warning: variable ‘flexibility’ set but not used [-Wunused-but-set-variable]
   int flexibility;
       ^
 Screen.c: In function ‘nxagentAdjustRandRXinerama’:
 Screen.c:3746:12: warning: unused variable ‘j’ [-Wunused-variable]
      int i, j;
             ^
 Screen.c: In function ‘nxagentSaveAreas’:
 Screen.c:4116:15: warning: variable ‘pDrawable’ set but not used [-Wunused-but-set-variable]
    DrawablePtr pDrawable;
                ^
 Screen.c: In function ‘nxagentRestoreAreas’:
 Screen.c:4236:15: warning: variable ‘pDrawable’ set but not used [-Wunused-but-set-variable]
    DrawablePtr pDrawable;
                ^
 ```