SDL_cocoaevents.m: fix build against SDK < 10.12 after commit 0dd7024d.
diff --git a/src/video/cocoa/SDL_cocoaevents.m b/src/video/cocoa/SDL_cocoaevents.m
index 5a0ab1f..7327869 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)
{