Fix more usages of NULL without including stdio.h.
diff --git a/configure b/configure
index 40f37de..992ff18 100755
--- a/configure
+++ b/configure
@@ -10881,6 +10881,7 @@
   cat confdefs.h - <<_ACEOF >conftest.$ac_ext
 /* end confdefs.h.  */
 
+#include <stdio.h>
 #include <sys/types.h>
 #include <netdb.h>
 #include <string.h>