Phobos addition formal review: std.experimental.allocator

[Brian Schott via Digitalmars-d]

On Sunday, 14 June 2015 at 14:30:00 UTC, Andrei Alexandrescu 
wrote:
> Interesting. Do you have a repro for this? Thanks! -- Andrei

Not yet, but while looking for one I found that this code 
triggers an assertion in Region.expand()
```
module test;

import std.experimental.allocator;
import std.stdio;

private alias AllocatorType = CAllocatorImpl!(AllocatorList!(
	n => Region!Mallocator(1024 * 4), NullAllocator));

struct Big {
	ubyte[1024] bytes;
}

void main(string[] args){
	auto a = new AllocatorType;
	foreach (i; 0 .. 100) {
		a.make!Big();
		writeln(i);
	}
}
```