WinRT: fixed bug whereby SDL would override an app's default orientation

WinRT apps can set a default, preferred orientation via a .appxmanifest file.
SDL was overriding this on app startup, and making the app use all possible
orientations (landscape and portrait).

Thanks to Eric Wing for the heads up on this!

include/SDL_opengles2_gl2platform.h

@@ -0,0 +1,30 @@
+#ifndef __gl2platform_h_
+#define __gl2platform_h_
+
+/* $Revision: 10602 $ on $Date:: 2010-03-04 22:35:34 -0800 #$ */
+
+/*
+ * This document is licensed under the SGI Free Software B License Version
+ * 2.0. For details, see http://oss.sgi.com/projects/FreeB/ .
+ */
+
+/* Platform-specific types and definitions for OpenGL ES 2.X  gl2.h
+ *
+ * Adopters may modify khrplatform.h and this file to suit their platform.
+ * You are encouraged to submit all modifications to the Khronos group so that
+ * they can be included in future versions of this file.  Please submit changes
+ * by sending them to the public Khronos Bugzilla (http://khronos.org/bugzilla)
+ * by filing a bug against product "OpenGL-ES" component "Registry".
+ */
+
+/*#include <KHR/khrplatform.h>*/
+
+#ifndef GL_APICALL
+#define GL_APICALL  KHRONOS_APICALL
+#endif
+
+#ifndef GL_APIENTRY
+#define GL_APIENTRY KHRONOS_APIENTRY
+#endif
+
+#endif /* __gl2platform_h_ */