Adjust the values of dirs1 and dirs2 so that rotate_and_place orients textures correctly

According to doc/lua_api.txt if paramtype2 == "facedir" the two least significant bits of parm2 orient the texture around the axis. For dirs1 (looking at a wall) these would be 0, 1, 2, 3 and for dirs2 (looking at the ceiling) 2, 1, 0, 3

pr #1808 against minetest/minetest