Fix some texture stuff: remove item_fence.png, use fence.png, remove...

Fix some texture stuff: remove item_fence.png, use fence.png, remove inexisting cactus.png from texture atlas (replace with nothing because cactus is rare)

src/content_mapnode.cpp

@@ -293,7 +293,7 @@ void content_mapnode_init()
 	f->dug_item = std::string("MaterialItem2 ")+itos(i)+" 1";
 	f->solidness = 0; // drawn separately, makes no faces
 	f->air_equivalent = true; // grass grows underneath
-	f->setInventoryTexture("item_fence.png");
+	f->setInventoryTexture("fence.png");
 	setWoodLikeDiggingProperties(f->digging_properties, 0.75);
 
 	i = CONTENT_RAIL;

src/tile.cpp

@@ -524,7 +524,6 @@ void TextureSource::buildMainAtlas()
 	sourcelist.push_back("cobble.png");
 	sourcelist.push_back("mossycobble.png");
 	sourcelist.push_back("gravel.png");
-	sourcelist.push_back("cactus.png");
 	sourcelist.push_back("jungletree.png");
 	
 	sourcelist.push_back("stone.png^mineral_coal.png");