fix Mac build with Xcode 8

Small issues in GHOST
- use NSApplicationDelegate protocol for our app delegate
- make sure NSApp is initialized before using
(cherry picked from commit df7be04ca6)

intern/ghost/intern/GHOST_SystemCocoa.mm

@@ -285,7 +285,7 @@ extern "C" int GHOST_HACK_getFirstFile(char buf[FIRSTFILEBUFLG])
  * CocoaAppDelegate
  * ObjC object to capture applicationShouldTerminate, and send quit event
  **/
-@interface CocoaAppDelegate : NSObject <NSFileManagerDelegate> {
+@interface CocoaAppDelegate : NSObject <NSApplicationDelegate> {
 	GHOST_SystemCocoa *systemCocoa;
 }
 - (void)setSystemCocoa:(GHOST_SystemCocoa *)sysCocoa;
@@ -412,8 +412,7 @@ GHOST_TSuccess GHOST_SystemCocoa::init()
 		}*/
 		
 		NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
-		if (NSApp == nil) {
-			[NSApplication sharedApplication];
+		[NSApplication sharedApplication]; // initializes	NSApp
 		
 		if ([NSApp mainMenu] == nil) {
 			NSMenu *mainMenubar = [[NSMenu alloc] init];
@@ -470,7 +469,7 @@ GHOST_TSuccess GHOST_SystemCocoa::init()
 			[NSApp setWindowsMenu:windowMenu];
 			[windowMenu release];
 		}
-		}
+
 		if ([NSApp delegate] == nil) {
 			CocoaAppDelegate *appDelegate = [[CocoaAppDelegate alloc] init];
 			[appDelegate setSystemCocoa:this];