Update the messages regarding too many (new) connections.

Changed "Too many connections from your IP" to have "[maxperip]" at the end.
Also create new setting and swap it with existing-one-during-development.

Long story short, we now have 3 different messages for these limits:

set::reject-message::too-many-connections
 "Too many connections from your IP [maxperip]"

set::reject-message::too-many-connections-ipv6-range
 "Too many connections from your IPv6 range ($prefix_addr/$prefix_len) [maxperip]"

set::reject-message::too-many-new-connections-ipv6-range
 "Too many new connections from this IPv6 range ($prefix_addr/$prefix_len) [connthrottle]"

So we explicitly mention whether it is maxperip or connthrottle limiting the
user, that should provide enough clue to the IRCOp if the user pastes the
message to them.

include/dynconf.h

@@ -160,6 +160,7 @@ struct Configuration {
 	BanTarget manual_ban_target;
 	char *reject_message_too_many_connections;
 	char *reject_message_too_many_connections_ipv6_range;
+	char *reject_message_too_many_new_connections_ipv6_range;
 	char *reject_message_server_full;
 	char *reject_message_unauthorized;
 	char *reject_message_kline;

include/h.h

@@ -529,6 +529,7 @@ extern const char *inetntop(int af, const void *in, char *local_dummy, size_t th
 
 extern void mask_ipv6_rawip(const char *src, int prefix, char *dst);
 extern const char *get_clone_mask_ipstr(Client *client, char *buf, size_t buflen);
+extern const char *format_ipv6_prefix_reject_message(const char *template, const char *masked_rawip, int prefix);
 
 extern void delletterfromstring(char *s, char letter);
 extern void addlettertodynamicstringsorted(char **str, char letter);