Drop ENABLE_GLES option

ENABLE_GLES predates forking Irrlicht. Its primary use was to distinguish Irrlicht-ogles from upstream version as Minetest could be compiled with either.
That's not necessary anymore and gets in the way sometimes.

src/client/tile.h

@@ -28,14 +28,12 @@ with this program; if not, write to the Free Software Foundation, Inc.,
 #include "util/numeric.h"
 #include "config.h"
 
-#if ENABLE_GLES
-#include <IVideoDriver.h>
-#endif
-
 class IGameDef;
 struct TileSpec;
 struct TileDef;
 
+namespace irr { namespace video { class IVideoDriver; } }
+
 typedef std::vector<video::SColor> Palette;
 
 /*
@@ -133,9 +131,7 @@ public:
 
 IWritableTextureSource *createTextureSource();
 
-#if ENABLE_GLES
 video::IImage *Align2Npot2(video::IImage *image, video::IVideoDriver *driver);
-#endif
 
 enum MaterialType{
 	TILE_MATERIAL_BASIC,