Rework MODE/RPL_CHANMODEIS handling for trailing args (#1661)

Some servers may send a colon even if the last parameter doesn't need it, currently this leads to issues with permission/mode tracking, as the core doesn't handle the colon properly.

This fix replaces reconstructing the parameter string with just passing a vector of the relevant parameters to CChan::SetModes() and adds overrides for CChan::SetModes() and CChan::ModeChange() that accept the vector instead.

Clean up uses of old CModeMessage::GetModes()

src/Client.cpp

@@ -1086,9 +1086,8 @@ bool CClient::OnJoinMessage(CJoinMessage& Message) {
 
 bool CClient::OnModeMessage(CModeMessage& Message) {
     CString sTarget = Message.GetTarget();
-    CString sModes = Message.GetModes();
 
-    if (m_pNetwork && m_pNetwork->IsChan(sTarget) && sModes.empty()) {
+    if (m_pNetwork && m_pNetwork->IsChan(sTarget) && !Message.HasModes()) {
         // If we are on that channel and already received a
         // /mode reply from the server, we can answer this
         // request ourself.