configure: Use 0 instead of NULL because NULL isn't defined.
diff --git a/configure b/configure
index 86adc79..9592bec 100755
--- a/configure
+++ b/configure
@@ -17686,13 +17686,13 @@
 main ()
 {
 
-    char *name=NULL;
+    char *name=0;
     struct hostent he;
     struct hostent *result;
-    char *buf=NULL;
+    char *buf=0;
     int bufsize=0;
     int res,errnr;
-    char *addr=NULL;
+    char *addr=0;
     int addrlen=0;
     int addrtype=0;
     res=gethostbyname_r(name,&he,buf,bufsize,&result,&errnr);