Exploratory change - WIP.

Added H support.

Added continue thread id tracking.

Working on getting $T stop notification reporting on all
but first stop after attach/launch.  This is to match behavior
seen from debugserver.

Currently broken: looks like Linux process monitoring may
be picking up the Resume to stop (the stop all implementation)
as exiting the thread.  The waitpid is getting a signal 5
which is getting transformed into a ptrace exit.  Could be the
wrong way to stop being issued.
Getting closer on stop-all-threads handling.

Now it properly recognizes a stop from the SignalHandler
and marks the thread.

The process is marked as stopped after the first thread
that stopped has its signal handling evaluated.  This may
be a problem if the "current" thread has not yet been marked
 as stopped - the $T handler may end up asking for the thread
stop reason for a different thread that is stopping (but hasn't)
had its stop registered yet) and then fail to produce a proper
$T/S response.

The issue now appears to be that the test is sending a hex
thread id with leading 0x from the test side.  debugserver
seemed to handle that fine.  llgs is not.  It is then returning
an error.