[PATCH] Add non-blocking Wait() for launched processes

[Edwin Vane]

  It seems to me that there's been a move from class abstractions for system entities like Path and Program. In the case of Path, we ended up with a bunch of free functions that operate on strings. I think leaving the type as "ProcessInfo" that can be operated on by free functions is consistent with that idea.

http://llvm-reviews.chandlerc.com/D1728