- Fix Linux build (huge thanks to Aokromes for testing as always)

- Some work towards resolving the crash on shutdown by implementing a shutdown task

--HG--
branch : trunk

src/server/game/Server/WorldSession.cpp

@@ -994,7 +994,7 @@ void WorldSession::ProcessQueryCallbacks()
     //! HandleAddFriendOpcode
     if (m_addFriendCallback.IsReady())
     {
-        std::string& param = m_addFriendCallback.GetParam();
+        const std::string& param = m_addFriendCallback.GetParam();
         m_addFriendCallback.GetResult(result);
         HandleAddFriendOpcodeCallBack(result, param);
         m_addFriendCallback.FreeResult();
@@ -1003,7 +1003,7 @@ void WorldSession::ProcessQueryCallbacks()
     //- HandleCharRenameOpcode
     if (m_charRenameCallback.IsReady())
     {
-        std::string& param = m_charRenameCallback.GetParam();
+        const std::string& param = m_charRenameCallback.GetParam();
         m_charRenameCallback.GetResult(result);
         HandleChangePlayerNameOpcodeCallBack(result, param);
         m_charRenameCallback.FreeResult();