Fix infinite climb

[TomyLobo]

There are (depending on the way you count) between 2 and 5 spots for this on da_cocaine.
I also found that this change prevents you from grabbing on to the rails below the roof of the shed on da_megachat. Since this never allowed you to climb anywhere, I think that is acceptable.

Also I made one of the wall angle checks a little less prone to rounding errors, which would have prevented climbing up walls that are almost, but not quite perpendicular to the ground.
One such surface is the side of the big truck on da_cocaine that faces the small truck.

_{There are client/server dependencies on this one, but they should be minor enough to not matter.}

[TomyLobo]

Are you aware of any places where people could (successfully) climb into a crouching position?
I'm not and I don't think it's possible due to the way these traces were always done, so I did not account for those.

[BSVino]

No, but my memory is terrible so you shouldn't count on it. I think I remember testing climb into crouch? Or did I code for it but never test it? Urgh, it was like six years ago ...

[TomyLobo]

heh, well i'm not aware of any.
I'll ask a few stunt-affine people about it if they can think of any.