[ffigen] Support more MACROS

[dcharkes]

We have support for macros that are direct constants:

• Support for constants defined by MACROS #534

But maybe we can do better and try to support more expressions and macros referring to macros.

• unknown type name 'FORCEINLINE' [Semantic Issue] #1057 (comment)

// minwindef.h

#define MAKEWORD(a, b)      ((WORD)(((BYTE)(((DWORD_PTR)(a)) & 0xff)) | ((WORD)((BYTE)(((DWORD_PTR)(b)) & 0xff))) << 8))
#define MAKELONG(a, b)      ((LONG)(((WORD)(((DWORD_PTR)(a)) & 0xffff)) | ((DWORD)((WORD)(((DWORD_PTR)(b)) & 0xffff))) << 16))
#define LOWORD(l)           ((WORD)(((DWORD_PTR)(l)) & 0xffff))
#define HIWORD(l)           ((WORD)((((DWORD_PTR)(l)) >> 16) & 0xffff))
#define LOBYTE(w)           ((BYTE)(((DWORD_PTR)(w)) & 0xff))
#define HIBYTE(w)           ((BYTE)((((DWORD_PTR)(w)) >> 8) & 0xff))

Maybe @mannprerak2 can give some insight on what would or would not be possible.

We're happy to receive contributions if anyone wants to take a stab at this. Relevant code:

• pkgs/ffigen/lib/src/header_parser/sub_parsers/macro_parser.dart

[mannprerak2]

I think we are already able to parse all non functional macros. Since we create a new cpp file and create variables for each macro and let libclang handle parsing and simply fetch that variable's value.

Any functional macros would require us to parse the underlying tokens directly.

Edit: I assume we're talking about parsing functional macros as helper functions in dart, anything constant at compile time should probably already work (unless there's an issue with include headers)