[CC1.62 SSP] Slab block is placed upper half in specific cases

Usually, when a turtle places a slab-block in front of him, the block is pleced lower half part.
But the block is placed upper half in two cases:

Case1:
- a turtle is headed in the "EAST" side.
- there is "not" a block in the bottom of front.

Case2:
- a turtle is headed in the "WEST" side.
- there is a block in the bottom of front.
- the placed slab-block is adjacent to a block in the front.

Sorry about my poor English. :(/>

Please see four attached images.
- case1-before.jpg
- case1-after.jpe
- case2-before.jpg
- case2-after.jpg

for i=1,4 do
  turtle.place()
  turtle.turnRight()
end

I'm not good at English, so I'm sorry if it is difficult for you to understand my English.

ComputerCraft1.63(for minecraft.1.6.4) has same bugs too.

I propose that more simple steps to reproduce bugs .

Case1:
1. Turns turtle's face to east side
2. Insert a slab-block in the turtle's inventory.
3. Run following code.

 turtle.up()
 turtle.place()

4. a slab-block is placed in the upper half.
There is a bug on the only east side.

Case2:
1. Turns turtle's face to west side
2. Insert two slab-block in the turtle's inventory.
3. Run following code.

 turtle.forward()
 turtle.place()
 turtle.back()
 turtle.place()

4. Second slab-block is placed in the upper half.
There is a bug on the only west side in this kind of situation.