Why can you cast an array to a pointer?

[Steven Schveighoffer]

Why is this still possible?

```d
int[] arr = new int[50];
auto ptr = cast(int *)arr;
```

1. casting is a blunt instrument, and can cause some really bad problems 
on code eveolution.
2. Literally easier to do arr.ptr instead of cast(T*)arr

Can we get rid of this? If you need the cast mechanism, and you really 
mean it, you can do `cast(T*)arr.ptr`

The biggest problem is that people using C API which take `char *` 
instead of `string` or whatnot, use `cast` and come to discord/etc with 
the inevitable problems this causes.

-Steve