Added reaper for commandline-launched processes.

GDBRemoteCommunicationServer::LaunchProcess () now uses the built-up
ProcessLaunchArgs rather than clearing and setting items from the
function arguments. I added setters for the arguments and launch
flags, which lldb-gdbserver uses for its specification of the
commandline-specified startup app (if one is specified).

LaunchProcess () also adds a new reaper monitor that it applies to
the launched process if no process monitor has already been applied.

This addresses an issue where the 'k' command would generate (possibly
false) warnings about not being able to positively state whether a
killed process actually terminated. GDBRemoteCommunicationServer now
definitely knows the disposition of its children.