MakeGW improvements

[CristiFati]

This is just side work as I was trying to add IFolderView functionality (to properly answer to [SO]: How to move desktop icons with python?) to win32comext.shell, and the process is annoying (well, since the 2^nd time I was running it from command line via -c, but having proper argument handling is the way to go).

As I was saying I was trying to add IFolderView, but the file no longer parses modern headers (tried ShObjIdl_core.h), due to __RPC__* specifiers (from rpcsal.h). It generates the files, but they don't compile due to (wrongly interpreting argument types - at least this is what I've seen so far).

I have some more changes (not included here) to the same file (basically getting rid of those specifiers), but the output files still need manual intervention (didn't reach (yet) a point where the file compiles (and works)).
Given the headache involved, I'm thinking I'm on the wrong path as there were no (significant) changes on the file file for a long long time, could it be a simpler variant?

As I also mentioned there, this is a side quest for #2181.

Last 2 commits made my life much easier, but there's still some work to be done, so that it works in an automated manner.

[mhammond]

This seems fine, thanks! I don't think this has generated code which compiled without modification for well over a decade!