Added header guards for SDLMain.h

--HG--
branch : SDL-1.2
extra : convert_revision : svn%3Ac70aab31-4412-0410-b14c-859654838e24/branches/SDL-1.2%403871

src/main/macosx/SDLMain.h

@@ -5,7 +5,12 @@
     Feel free to customize this file to suit your needs
 */
 
+#ifndef _SDLMain_h_
+#define _SDLMain_h_
+
 #import <Cocoa/Cocoa.h>
 
 @interface SDLMain : NSObject
 @end
+
+#endif /* _SDLMain_h_ */