mkapi: untangle types & typedefs

[jepler]

Description

There's a lot of confusion in mkapi due to ad-hoc handling of C types (structures & typedefs).

Here's a plan to improve things:

Getting rid of the use of strings to carry C type information at all. Instead, introduce class Struct and class Scalar to go with class Ptr and class Array. An Argument object's type field would always be a Scalar, Struct, Ptr, or Array.

The return_ property of a function should similarly be a "C type object" (Struct/Scalar/Ptr/Array).

Add a single function that will look up the type information from a C type string for use in argument & return value handling, instead of smearing the 'check if it's a struct / check if it's a typedef' across the whole system.

This will make for some churn in mkapi, but overall it should simplify things.

Implementation

I intend to implement this feature and would submit a Pull Request if desirable

Code of Conduct

Yes, I agree