- Deprecated FProcHandle::Close() in favor of existing FPlatformProcess::CloseProc() (symmetric to FPlatformProcess::CreateProc()).
- Linux: made FProcHandle instances safe to pass by value.
- Linux: added support for "fire and forget" children, which will not leave zombies (at the expense of extra threads and a leaked thread handle).
- Extended TestPAL with tests for most of the above functionality.
#codereview Michael.Trepka, Josh.Adams, Robert.Manuszewski, Jaroslaw.Surowiec
[CL 2476050 by Dmitry Rekman in Main branch]