restore old plan 9 property that when the

last thread exits the main proc, the remaining
program ends up in the background and the
program appears to have exited.

src/libthread/FreeBSD.c

@@ -346,6 +346,13 @@ _pthreadinit(void)
 	signal(SIGUSR2, sigusr2handler);
 }
 
+void
+_threadpexit(void)
+{
+	_exit(0);
+}
+
+
 /*
  * FreeBSD 4 and earlier needs the context functions.
  */