top: let's not pretend top can catch SIGKILL & SIGSTOP

While there was no harm done setting a handler for the
above two signals, they are in fact uncatchable. Thus,
whenever we ran with valgrind we're politely reminded.

Signed-off-by: Jim Warner <james.warner@comcast.net>

top/top.c

@@ -3342,6 +3342,8 @@ static void before (char *me) {
          default:
             sa.sa_handler = sig_abexit;
             break;
+         case SIGKILL: case SIGSTOP:
+         // because uncatchable, fall through
          case SIGCHLD: // we can't catch this
             continue;  // when opening a pipe
       }