Emit handles as void* not IntPtr

[Rafael Rivera]

Rust currently emits isize/usize integers as a result of decomposing our synthetic handle types and encountering IntPtr/UIntPtr. Rust would now like to emit pointers to better align with its core handle type, but it cannot differentiate between legitimate pointer-sized integers (e.g. LRESULT) and handles (e.g. HMODULE).

The proposed change is to emit all handles with their original pointer type.

// Before
public struct HMODULE
{
   public IntPtr Value;
}

// After
public struct HMODULE
{
   public unsafe void* Value;
}

See also: microsoft/windows-rs#3093

[Kenny Kerr]

This is substantiated by the fact that wtypes.h, and many others, actually defines these as pointers so this is just asking that the metadata is faithful to the original definitions, for example:

typedef void * HANDLE;
typedef void *HMODULE;

typedef void *HINSTANCE;

typedef void *HTASK;

typedef void *HKEY;

typedef void *HDESK;

typedef void *HMF;

typedef void *HEMF;

typedef void *HPEN;

typedef void *HRSRC;

typedef void *HSTR;

typedef void *HWINSTA;

typedef void *HKL;

typedef void *HGDIOBJ;

[Mike Battista]

These and others are declared with the DECLARE_HANDLE macro. Should all of these be void*?

[Kenny Kerr]

Yes, the underlying handle type for DECLARE_HANDLE are all pointers and void* is the generic underlying type for such handles.