prevent crash in gpu_draw.c, so tilemode might not have GLSL/GPU features

/* for tiles, copy only part of image into buffer */
	if (GTS.tilemode) {
		return 0; //disabled for now, it causes crashes
	
See tracker issue here:
http://projects.blender.org/tracker/index.php?func=detail&aid=17819&group_id=9&atid=125

source/blender/gpu/intern/gpu_draw.c

@@ -448,6 +448,9 @@ int GPU_verify_image(Image *ima, int tftile, int tfmode, int compare)
 
 	/* for tiles, copy only part of image into buffer */
 	if (GTS.tilemode) {
+		return 0; //disabled for now, it causes crashes
+		//see http://projects.blender.org/tracker/index.php?func=detail&aid=17819&group_id=9&atid=125
+
 		tilerect= MEM_mallocN(rectw*recth*sizeof(*tilerect), "tilerect");
 
 		for (y=0; y<recth; y++) {