Change analysis into proper passes and rearrange data

[gkoz]

Calling only the analyzers you need from codegen seems limiting and requires workarounds to avoid duplicate work.

A more robust scheme would be to do the analysis first and then let the codegen use that data. Expected benefits:

• parser cleanup, by moving the patching logic to a separate stage,
• library cleanup, by removing the bits of analysis from it,
• analysis stages can rely on the data from earlier ones and agree on viral blacklisting (commenting out) effects,
• possibly, weaker coupling between stages.

This is just a first approximation, I've not thought about the ways to organize the data. TypeId would probably turn into DefId. We could probably learn a thing or two from rustc.

[EPashkin]

Good long-term objective, but I do not have any ideas how to do it.

[gkoz]

In the (still in progress) ffi_ng branch I'm translating the "gir" representation created by the parser into the "foreign" one. The "foreign" analysis is going to be responsible for applying quirks, creating helper types for unions, tracking visibility and other contagious properties, generating rust FFI type strings etc. The generator just has to iterate through the definitions and do some format!s.

[gkoz]

I think now's a good time to try implementing some changes to this effect. I intend to continue work on the ffi_ng branch soon.