Fixed an issue in "SBError SBProcess::Destroy ()" where it wasn't properly

checking the validity of the shared pointer prior to using it.

Fixed the GDB remote plug-in to once again watch for a reply from the "k" 
packet, and fixed the logic to make sure the thread requesting the kill
and the async thread play nice (and very quickly) by synchronizing the
packet sending and reply. I also tweaked some of the shut down packet
("k" kill, "D" detach, and the halt packet) to make sure they do the right
thing.

Fixed "StateType Process::WaitForProcessStopPrivate (...)" to correctly pass
the timeout along to WaitForStateChangedEventsPrivate() and made the function
behave correctly with respect to timing out.

Added separate STDIN, STDOUT, and STDERR support to debugserver. Also added
the start of being able to set the working directory for the inferior process.

llvm-svn: 124049