Named unittests

[Robert burner Schadek via Digitalmars-d]

I have PR 
https://github.com/D-Programming-Language/phobos/pull/2995 open 
since October 2014.

it includes:
* extensible haskell like quickcheck
* benchmarking with "names" and record keeping to see progress
* offline tool to plot benchmark results with gnuplot
* most std.string functions already have benchmarks
* makefiles got a new BUILD=benchmark

IMO continuous benchmarking of phobos is a must-have feature and 
a nice marketing tool ( benchmark graphs on dlang.org). Something 
similar to quickcheck is equally important, to get the test input 
you didn't expect.

I got one and a half comments so far.