fixed compilation warning

modules/gui/macosx/fspanel.h

@@ -37,7 +37,7 @@
     int i_device;
 }
 - (id)initWithContentRect: (NSRect)contentRect
-                styleMask: (unsigned int)aStyle
+                styleMask: (NSUInteger)aStyle
                   backing: (NSBackingStoreType)bufferingType
                     defer: (BOOL)flag;
 - (void)awakeFromNib;

modules/gui/macosx/fspanel.m

@@ -41,7 +41,7 @@
 @implementation VLCFSPanel
 /* We override this initializer so we can set the NSBorderlessWindowMask styleMask, and set a few other important settings */
 - (id)initWithContentRect:(NSRect)contentRect 
-                styleMask:(NSInteger)aStyle 
+                styleMask:(NSUInteger)aStyle 
                   backing:(NSBackingStoreType)bufferingType 
                     defer:(BOOL)flag
 {