Sneaking thinks nodeboxes are full nodes

[Calinou]

If you sneak on a nodebox, you will collide with the node like if it was a full node.

[ShadowNinja]

Duplicate of #127

[Calinou]

Closed #127 since this is a more accurate report; didn't see.

[sapier]

Granularity of collision handling in minetest is node level this most likely is a engine limitation issue.
Improved collision handling would help but this requires more CPU power so it'd result in slower minetest.

[gregorycu]

This is not based on CD, just based on poor sneaking code. I tried a few things, but I couldn't fix this without introducing other bugs.