Core: Add new system for parallelizing client packet processing. Handle WorldSession updates in Map::Update() where we are safe to proceed. Patch by Ambal.

(And clean up tabs and whitespace while rummaging around in there)
Closes issue 5084.

--HG--
branch : trunk

src/server/game/Server/Protocol/Opcodes.h

@@ -1359,12 +1359,20 @@ enum SessionStatus
     STATUS_UNHANDLED,                                       // Opcode not handled yet
 };
 
+enum PacketProcessing
+{
+    PROCESS_INPLACE = 0,                                    //process packet whenever we receive it - mostly for non-handled or non-implemented packets
+    PROCESS_THREADUNSAFE,                                   //packet is not thread-safe - process it in World::UpdateSessions()
+    PROCESS_THREADSAFE                                      //packet is thread-safe - process it in Map::Update()
+};
+
 class WorldPacket;
 
 struct OpcodeHandler
 {
     char const* name;
     SessionStatus status;
+    PacketProcessing packetProcessing;
     void (WorldSession::*handler)(WorldPacket& recvPacket);
 };