CLOFF_JUMPWALL/FLOOR/CEILING

[Major Cooke]

Pull request.

I found CLOFF_JUMP_ON_MISS was in particularly too general for what I needed, so I came up with this to further it.

This relies upon either 'missing' (with or without flags) a target, or using CLOFF_ALLOWNULL and bypassing the target altogether (Make use of A_Face* functions and stick a 0 in for the pitch limit -- otherwise it won't adjust pitch).