Add more states from /proc/[pid]/stat

from man 5 proc on /proc/[pid]/stat, we see:
              (3) state  %c
                     One of the following characters, indicating process state:

                     R      Running

                     S      Sleeping in an interruptible wait

                     D      Waiting in uninterruptible disk sleep

                     Z      Zombie

                     T      Stopped (on a signal) or (before Linux 2.6.33) trace stopped

                     t      Tracing stop (Linux 2.6.33 onward)

                     W      Paging (only before Linux 2.6.0)

                     X      Dead (from Linux 2.6.0 onward)

                     x      Dead (Linux 2.6.33 to 3.13 only)

                     K      Wakekill (Linux 2.6.33 to 3.13 only)

                     W      Waking (Linux 2.6.33 to 3.13 only)

                     P      Parked (Linux 3.9 to 3.13 only)

                     I      Idle (Linux 4.14 onward)

Of the states there, 't' and 'X' are the only ones missing, so add them.
I hit these when strace'ing a test.

Change-Id: I3048e82fc5265c1f701538ae209183ecf8a961be
Signed-off-by: Austin Schuh <austin.schuh@bluerivertech.com>
Signed-off-by: James Kuszmaul <james.kuszmaul@bluerivertech.com>
diff --git a/aos/util/top.cc b/aos/util/top.cc
index 10ebd4d..8a78609 100644
--- a/aos/util/top.cc
+++ b/aos/util/top.cc
@@ -209,6 +209,10 @@
       return ThreadState::ZOMBIE;
     case 'I':
       return ThreadState::IDLE;
+    case 'X':
+      return ThreadState::DEAD;
+    case 't':
+      return ThreadState::TRACING_STOP;
     default:
       LOG(FATAL) << "Invalid thread state character: " << state;
   }