wall render bug in 1.14

when there is a wall combination like:

[code:1:e2b292cb9d]
w w !
w w w
! w !
[/code:1:e2b292cb9d]

it uses the wrong wall image. w = wall, ! = not wall.

I think it's caused by a duplicated image in the default skin bmp.

Nice discovery. I had never noticed it.

Playing around I noticed that if you start out with this layout:

! w !
www
! w !

Then put a wall on the northwest corner to get the setup zzz points out, you can see the "dramatic" change happen.