Fix sign v zero extension error in handling IP address

I switch to the git version of chrony. Accidently this version did not
talk to by lokal server at 192.168.192.4. Instead it continuosly tried
255.255.192.4 :-( .

Tracked that down to "char", "unsigned char" issue in nameserv.c:

nameserv.c

@@ -39,7 +39,7 @@ unsigned long
 DNS_Name2IPAddress(const char *name)
 {
   struct hostent *host;
-  char *address0;
+  unsigned char *address0;
   unsigned long result;
 
   host = gethostbyname(name);