[Issue 24793] New: Allow implicit conversion of const pointers to void*

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=24793

          Issue ID: 24793
           Summary: Allow implicit conversion of const pointers to void*
           Product: D
           Version: D2
          Hardware: All
                OS: All
            Status: NEW
          Severity: enhancement
          Priority: P3
         Component: dmd
          Assignee: nobody at puremagic.com
          Reporter: dkorpel at live.nl

When interfacing with C APIs, I sometimes find myself casting away const on
void pointers.

```
void main()
{
    const int* x = cast(int*) malloc(4);
    free(cast(void*) x);
}

struct Console
{
    HANDLE handle; // HANDLE = void* on Windows

    void write(string s) const
    {
        WriteConsoleW(cast(void*) this.handle, ...);
    }
}
```

This should be unnecessary. With void* you already completely give up on type
safety, so why be persnickety about `const`?

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