macosx/fspanel: remove some dead code

modules/gui/macosx/fspanel.h

@@ -69,7 +69,6 @@
 - (void)mouseDown: (NSEvent *)theEvent;
 - (void)mouseDragged: (NSEvent *)theEvent;
 
-- (BOOL)isDisplayed;
 - (void)setVoutWasUpdated: (int)i_screen;
 @end
 

modules/gui/macosx/fspanel.m

@@ -367,11 +367,6 @@
     [self setFrameOrigin:point];
 }
 
-- (BOOL)isDisplayed
-{
-    return b_displayed;
-}
-
 - (void)setVoutWasUpdated: (int)i_newdevice;
 {
     b_voutWasUpdated = YES;