Added a real GUI message box to Sys_ErrorDialog() on Mac OS X.

Fixes Bugzilla #3654.

code/sys/sys_cocoa.m

@@ -0,0 +1,40 @@
+/*
+===========================================================================
+Copyright (C) 1999-2005 Id Software, Inc.
+
+This file is part of Quake III Arena source code.
+
+Quake III Arena source code is free software; you can redistribute it
+and/or modify it under the terms of the GNU General Public License as
+published by the Free Software Foundation; either version 2 of the License,
+or (at your option) any later version.
+
+Quake III Arena source code is distributed in the hope that it will be
+useful, but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with Quake III Arena source code; if not, write to the Free Software
+Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
+===========================================================================
+*/
+
+#ifndef MACOS_X
+#error This file is for Mac OS X only. You probably should not compile it.
+#endif
+
+// Please note that this file is just some Mac-specific bits. Most of the
+//  Mac OS X code is shared with other Unix platforms in sys_unix.c ...
+
+#import <Cocoa/Cocoa.h>
+
+void Sys_Cocoa_MsgBox( const char *text )
+{
+	NSRunInformationalAlertPanel(@"ioquake3", 
+	                             [NSString stringWithUTF8String:text],
+	                             @"OK", nil, nil);
+}
+
+// end of sys_cocoa.m ...
+