SDL: SDL_cocoaevents.m: fix build against SDK < 10.12 after commit 0dd7024d.

From 2f248a2a31c3323ecc37c00ad5e269e347ae392a Mon Sep 17 00:00:00 2001
From: Ozkan Sezer <[EMAIL REDACTED]>
Date: Fri, 11 Jun 2021 04:00:32 +0300
Subject: [PATCH] SDL_cocoaevents.m: fix build against SDK < 10.12 after commit
 0dd7024d.

---
 src/video/cocoa/SDL_cocoaevents.m | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/src/video/cocoa/SDL_cocoaevents.m b/src/video/cocoa/SDL_cocoaevents.m
index 5a0ab1fb4..732786988 100644
--- a/src/video/cocoa/SDL_cocoaevents.m
+++ b/src/video/cocoa/SDL_cocoaevents.m
@@ -35,6 +35,9 @@
 #ifndef NSAppKitVersionNumber10_8
 #define NSAppKitVersionNumber10_8 1187
 #endif
+#ifndef MAC_OS_X_VERSION_10_12
+#define NSEventTypeApplicationDefined NSApplicationDefined
+#endif
 
 static SDL_Window *FindSDLWindowForNSWindow(NSWindow *win)
 {