[Suggestion] Curve the npeghole primitives

[Max Murtazin]

The main issue is that the suggested design doesn't work in primitive substitution mode.

Most of the holes in beams are made using the connhole.dat primitive, and when it changes shape, the npeghole has to also adapt.
Many of the npeg primitives are today made using cyli primitives.

Or all beams will end up looking like this:

I already mentioned that this variant is just a plain shape, just a plain model. I am going to make it work with primitive substitution once properly done