macosx: Declare all of MainWindow's methods in its interfaces

Fixes compiler warnings for a few methods without declarations called
before their definitions.
Signed-off-by: Felix Paul Kühne <fkuehne@videolan.org>

modules/gui/macosx/MainWindow.h

@@ -148,7 +148,11 @@
 + (VLCMainWindow *)sharedInstance;
 
 - (IBAction)play:(id)sender;
+- (IBAction)prev:(id)sender;
+- (IBAction)backward:(id)sender;
 - (IBAction)bwd:(id)sender;
+- (IBAction)next:(id)sender;
+- (IBAction)forward:(id)sender;
 - (IBAction)fwd:(id)sender;
 - (IBAction)stop:(id)sender;
 - (IBAction)togglePlaylist:(id)sender;

modules/gui/macosx/MainWindow.m

@@ -42,6 +42,25 @@
 #import <vlc_services_discovery.h>
 #import <vlc_aout_intf.h>
 
+@interface VLCMainWindow ()
+- (void)addJumpButtons:(BOOL)b_fast;
+- (void)removeJumpButtons:(BOOL)b_fast;
+- (void)addPlaymodeButtons:(BOOL)b_fast;
+- (void)removePlaymodeButtons:(BOOL)b_fast;
+
+- (void)resetPreviousButton;
+- (void)resetBackwardSkip;
+- (void)resetNextButton;
+- (void)resetForwardSkip;
+- (void)resizePlaylistAfterCollapse;
+- (void)makeSplitViewVisible;
+- (void)makeSplitViewHidden;
+
+- (NSRect)customConstrainFrameRect: (NSRect)frameRect toScreen: (NSScreen*)screen;
+
+- (NSString *)getCurrentTimeAsString:(input_thread_t *)p_input;
+@end
+
 @implementation VLCMainWindow
 static const float f_min_video_height = 70.0;