Be consistent: use GL_TEXTURE_3D not GL_TEXTURE_3D_EXT.

src/textures.c

@@ -109,7 +109,7 @@ int txbind( Texture *tx, int *enabled )
   }
 
 #ifdef GL_TEXTURE_3D
-  txtarget = (tx->flags & TXF_3D) ? GL_TEXTURE_3D_EXT : GL_TEXTURE_2D;
+  txtarget = (tx->flags & TXF_3D) ? GL_TEXTURE_3D : GL_TEXTURE_2D;
 
 #else
   txtarget = GL_TEXTURE_2D;