Added ability to spawn process with specific user, under linux
Fixed edge case memory leak caused when we were trying to QueueUserAPC to a thread we were already on, which also caused a 3 second delay.
Changed WindowsRunLoop, to detect bad HANDLEs, and event an error on them, and remove them from list
Fixed linux bug, where a spawned child called 'exit' instead of '_exit' in an error condition
a3f69396f6