cgogen generate variable-argument lists code

[xlab]

cgogen generate variable-argument lists code

[xlab]

Surely, I usually just ignore these functions in manifest.
When CGO will support variadic argument lists I'll implement that in cgogen too. There is an idea of implementing a helper for that in .c and .h helpers, but variadics in C are not portable and I have no enough motivation to deal with this problem.

[lotodore]

Code generation from https://github.com/cimgui/cimgui would heavily depend on this feature, because cimgui is pretty much unusable without variadic argument lists. Right now, it cannot be used at all.

Is there any chance that variadic argument lists might still be implemented?

[xlab]

@lotodore
golang/go#975 no movement there for 6 freaking years :(

So it has to generate C bridge functions, if we want to have this support. Cgogen already generates bridges for the callbacks.. So it might worth a shot.