cocoa_common: accept window drag event from the whole window surface

Change the window to accept mouse drag events not only on the title
bar, but also on the rest of the window surface; this includes the
video area.

It looks like the changing of the window mask resets the behaviour
specified in the delegate method, probably due to some strange
interaction with NSBorderlessWindow. For this reason call
-setPresentationOptions in the -fullscreen method to remind cocoa the
behaviour we want.

libvo/cocoa_common.m

@@ -368,6 +368,7 @@ void create_menu()
         [self setLevel:s->fullscreen_window_level];
         vo_fs = VO_TRUE;
         vo_cocoa_display_cursor(0);
+        [self setMovableByWindowBackground: NO];
     } else {
         [NSApp setPresentationOptions:NSApplicationPresentationDefault];
         [self setHasShadow:YES];
@@ -382,6 +383,7 @@ void create_menu()
         [self setLevel:s->windowed_window_level];
         vo_fs = VO_FALSE;
         vo_cocoa_display_cursor(1);
+        [self setMovableByWindowBackground: YES];
     }
 }
 
@@ -399,6 +401,12 @@ void create_menu()
     return NO;
 }
 
+- (BOOL) isMovableByWindowBackground
+{
+    // this is only valid as a starting value. it will be rewritten in the -fullscreen method.
+    return !vo_fs;
+}
+
 - (void) handleQuitEvent:(NSAppleEventDescriptor*)e withReplyEvent:(NSAppleEventDescriptor*)r
 {
     mplayer_put_key(l_vo->key_fifo, KEY_CLOSE_WIN);