call for GC benchmarks

[Martin Nowak via Digitalmars-d]

I'd like to have a few more real world GC benchmarks in druntime.
The current ones are all rather micro-benchmarks, some of them don't 
even create garbage.

So if someone has a program that is heavily GC limited, I'd be 
interested in seeing that converted to a benchmark.

Made the start with one 
https://github.com/D-Programming-Language/druntime/pull/1078 that 
resembles a mysql to mongodb importer I wrote recently.