Switched to LinkedList for channels.

Switched to LinkedList data structure for channels, since I do not think
the ArrayList offers any performance improvements and likely needs more
memory. Besides, the specs don't specify any kind of intelligent lookup,
so there is no need for random access performance or ordering searching.

src/net/java/sip/communicator/impl/protocol/irc/IrcStack.java

@@ -293,7 +293,7 @@ public List<String> getServerChatRoomList()
         {
             if (this.channellist.instance == null)
             {
-                List<String> list = new ArrayList<String>();
+                List<String> list = new LinkedList<String>();
                 synchronized (list)
                 {
                     try
@@ -460,6 +460,7 @@ public void onFailure(Exception e)
                     });
                 // Wait until async channel join operation has finished.
                 joinSignal.wait();
+                // TODO How to handle 471: Channel is full (reached set user limit)?
                 if (isJoined(chatroom))
                 {
                     // In case waiting ends with successful join