Add support for arrays + INOUT arguments

[Place1]

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[Place1]

@romgrk I'm struggling a little bit with INOUT arguments. You can see my approach in this PR.

I'm trying to encapsule the logic and memory management of IN/OUT args in a Parameter class similar to your approach in node-gtk. I'd love some tips of maybe even a breakdown of how it should work to get me over the last bump.

[romgrk]

Awesome if it works for you, but on my side, arithemics on pointers are byte based. E.g. if I add (void*)0x2000 + (int)1, I get (void*)0x2008. That's the reason for casting to a ulong.

[romgrk]

Do you have more specific questions? I see the general flow of the thing, but I'd need to understand the whole relevant parts of the codebase to spot specific bugs/issues.

General observations:

• INOUT-arguments are similar to OUT-arguments in that you always need to add a level of indirection to them. In node-gtk, we first fill the GIArgument as for an IN-argument, then store that value in a pointer on the stack, then point the GIArgument to that stack-pointer.
• You will eventually need a FreeGIArgument function, to deallocate any resources created during the function call. (for reference, here is PyGObject version: https://gitlab.gnome.org/GNOME/pygobject/blob/master/gi/pygi-argument.c#L1005-1271)
• You're allocating your Out/In/InOutParameter instances on the heap. Function calling is a "hot" part of the bindings, if it's possible to do so you should use the stack only.