* Merge io.InStream and io.OutStream into io.File
 * Introduce io.OutStream and io.InStream interfaces
   - io.File implements both of these
 * Move mem.IncrementingAllocator to heap.IncrementingAllocator

Instead of:

```
%return std.io.stderr.printf("hello\n");
```

now do:

```
std.debug.warn("hello\n");
```

To print to stdout, see `io.getStdOut()`.

 * Rename std.ArrayList.resizeDown to std.ArrayList.shrink.