Enable chanmode +r, fix bug with registering channels

irc/channel.go

 	if channel.flags[Moderated] && !channel.clientIsAtLeastNoMutex(client, Voice) {
 		return false
 	}
+	if channel.flags[RegisteredOnly] && client.account == &NoAccount {
+		return false
+	}
 	return true
 }
 

irc/chanserv.go

 			}
 
 			account := client.account
-			if account == nil {
+			if account == &NoAccount {
 				client.ChanServNotice("You must be logged in to register a channel")
 				return nil
 			}

irc/help.go

 
 Oragono supports the following channel modes:
 
-= Type A - list modes =
-
-  +b  |  Client masks that are banned from the channel.
+  +b  |  Client masks that are banned from the channel (e.g. *!*@127.0.0.1)
   +e  |  Client masks that are exempted from bans.
   +I  |  Client masks that are exempted from the invite-only flag.
-
-= Type C - setting modes with a parameter =
-
-  +l  |  Client join limit for the channel.
-  +k  |  Key required when joining the channel.
-
-= Type D - flag modes =
-
   +i  |  Invite-only mode, only invited clients can join the channel.
+  +k  |  Key required when joining the channel.
+  +l  |  Client join limit for the channel.
   +m  |  Moderated mode, only privileged clients can talk on the channel.
   +n  |  No-outside-messages mode, only users that are on the channel can send
       |  messages to it.
-  +t  |  Only channel opers can modify the topic.
+  +r  |  Only registered users can talk in the channel.
   +s  |  Secret mode, channel won't show up in /LIST or whois replies.
+  +t  |  Only channel opers can modify the topic.
 
 = Prefixes =
 
 		text: `MODE <target> [<modestring> [<mode arguments>...]]
 
 Sets and removes modes from the given target. For more specific information on
-mode characters, see the help for "cmode" and "umode".`,
+mode characters, see the help for "modes".`,
 	},
 	"monitor": {
 		text: `MONITOR <subcmd>
 	},
 
 	// Informational
+	"modes": {
+		text: cmodeHelpText + "\n\n" + umodeHelpText,
+	},
 	"cmode": {
 		text: cmodeHelpText,
 	},

irc/modes.go

 	Moderated       Mode = 'm' // flag
 	NoOutside       Mode = 'n' // flag
 	OpOnlyTopic     Mode = 't' // flag
+	RegisteredOnly  Mode = 'r' // flag
 	Secret          Mode = 's' // flag
 	UserLimit       Mode = 'l' // flag arg
 )
 			}
 			applied = append(applied, change)
 
-		case InviteOnly, Moderated, NoOutside, OpOnlyTopic, Secret, ChanRoleplaying:
+		case InviteOnly, Moderated, NoOutside, OpOnlyTopic, RegisteredOnly, Secret, ChanRoleplaying:
 			switch change.op {
 			case Add:
 				if channel.flags[change.mode] {

irc/server.go

 				client.Send(nil, server.name, ERR_NOSUCHCHANNEL, client.nick, targetString, "No such channel")
 				continue
 			}
+			if !channel.CanSpeak(client) {
+				client.Send(nil, client.server.name, ERR_CANNOTSENDTOCHAN, channel.name, "Cannot send to channel")
+				continue
+			}
 			msgid := server.generateMessageID()
 			channel.SplitPrivMsg(msgid, lowestPrefix, clientOnlyTags, client, splitMsg)
 		} else {
 				client.Send(nil, server.name, ERR_NOSUCHCHANNEL, client.nick, targetString, "No such channel")
 				continue
 			}
+			if !channel.CanSpeak(client) {
+				client.Send(nil, client.server.name, ERR_CANNOTSENDTOCHAN, channel.name, "Cannot send to channel")
+				continue
+			}
 			msgid := server.generateMessageID()
 
 			channel.TagMsg(msgid, lowestPrefix, clientOnlyTags, client)
 				// errors silently ignored with NOTICE as per RFC
 				continue
 			}
+			if !channel.CanSpeak(client) {
+				// errors silently ignored with NOTICE as per RFC
+				continue
+			}
 			msgid := server.generateMessageID()
 			channel.SplitNotice(msgid, lowestPrefix, clientOnlyTags, client, splitMsg)
 		} else {