Core/Scripts: Changed chat command handlers to take ChatHandler* as an argument, instead of as 'this'.

Fixes commandscripts so it can be used to add custom commands without editing chat.h, chat.cpp or levelX.cpp files.

Patch by Accel
Closes issue 4629

--HG--
branch : trunk

src/server/game/Chat/Chat.h

@@ -38,7 +38,7 @@ class ChatCommand
         const char *       Name;
         uint32             SecurityLevel;                   // function pointer required correct align (use uint32)
         bool               AllowConsole;
-        bool (ChatHandler::*Handler)(const char* args);
+        bool (*Handler)(ChatHandler*, const char* args);
         std::string        Help;
         ChatCommand *      ChildCommands;
 };