Parallel execution of unittests

[Dicebot via Digitalmars-d]

I believe only missing step right now is propagation of UDA's to 
RTInfo when demanded. Everything else can be done as Phobos 
solution.

And if requirement to have all modules transitively accessible 
from root one is acceptable it can be already done with 
http://dlang.org/traits.html#getUnitTests

Simplicity of D unit tests is their best feature.