DIP80: phobos additions

[Andrei Alexandrescu via Digitalmars-d]

On 6/9/15 11:42 AM, Dennis Ritchie wrote:
> "And finally `std.bigint` offers good (but not outstanding) performance."

BigInt should use reference counting. Its current approach to allocating 
new memory for everything is a liability. Could someone file a report 
for this please. -- Andrei