K. Piche:  Unofficial patch for mailx.

--- ./dotlock.c.orig      2005-09-18 20:28:20.000000000 -0400
+++ ./dotlock.c   2005-09-18 20:26:59.000000000 -0400
@@ -47,6 +47,7 @@
 #include <errno.h>
 #include <signal.h>

+#include "def.h"
 #include "extern.h"

 #ifndef O_SYNC