thread.c: threadstatus improve output and implement P9 stop
thread.c: threadstatus improve output and implement P9 stop

There's no point compressing status down to a single letter. Add
letters for each mode we are intereted in. Add the P9 stop state.

Signed-off-by: Nicholas Piggin <24829078df5003d9dd1dd871ca2aeb0b1cf95ef4@gmail.com>

open-power/pdbg,open-power/pdbg,open-power/pdbg