Use IPv4 format for IPv4-mapped addresses

For instance, use "127.0.0.1" for IPv4 loopback instead of
"::ffff:127.0.0.1".

Simplifies use of econfig key privip: plain dotted decimal now just
works regardless of IPv6 use, no need to add the IPv4-mapped form.

Also affects how addresses are logged and shown to players, and nation
selector ip.  Nicer that way.

src/lib/global/constants.c

@@ -41,7 +41,7 @@ char *privname = "Deity forgot to edit econfig";
 /* E-mail of the deity */
 char *privlog = "careless@invalid";
 /* Divine hosts and networks */
-char *privip = "127.0.0.1 ::1 ::ffff:127.0.0.1";
+char *privip = "127.0.0.1 ::1";
 
 char *post_crash_dump_hook = "";