Set channel mode +r when a channel is registered

ChanServ sends FMODE to mark a registered channel +r (the m_services
c_registered mode), and -r on drop. Sourced from our server, which the
ircd requires for that mode, with a low TS so it applies to the existing
channel.

src/proto/mod.rs

@@ -38,6 +38,9 @@ pub enum NetAction {
     // Force a user's nick (SVSNICK), e.g. renaming to a guest nick on logout.
     // The protocol stamps the new nick's timestamp.
     ForceNick { uid: String, nick: String },
+    // Set channel modes from services, e.g. +r on a registered channel. The
+    // protocol stamps a timestamp the ircd will accept.
+    ChannelMode { channel: String, modes: String },
     Raw(String),
     // Internal only, never serialized to the wire: a registration whose password
     // still needs its (expensive) key derivation. The link layer runs the