[C++] Disable potion in duel

//@Source/Game/char_item.cpp
//1.) Add header:
    #include "pvp.h"
//2.) Search:
    case USE_POTION:
//3.) Add after:
    if (CPVPManager::instance().IsFighting(GetPlayerID()))
    {
        switch (item->GetVnum())
        {
            case 27001:
            case 27002:
            case 27003:
            case 27004:
            case 27005:
            case 27006:
            ChatPacket(CHAT_TYPE_INFO, "You can not use potions in a duel!");
            return false;
            break;
        }
    }
//@Source/Game/pvp.cpp
//4.) Search:
    void CPVPManager::ConnectEx(LPCHARACTER pkChr, bool bDisconnect)
//5.) Add before:
bool CPVPManager::IsFighting(LPCHARACTER pkChr)
{
    if (!pkChr)
        return false;

    return IsFighting(pkChr->GetPlayerID());
}

bool CPVPManager::IsFighting(DWORD dwPID)
{
    CPVPSetMap::iterator it = m_map_pkPVPSetByID.find(dwPID);

    if (it == m_map_pkPVPSetByID.end())
        return false;

    TR1_NS::unordered_set<CPVP*>::iterator it2 = it->second.begin();

    while (it2 != it->second.end())
    {
        CPVP * pkPVP = *it2++;
        if (pkPVP->IsFight())
            return true;
    }

    return false;
}
//@Source/Game/pvp.h
//4.) Search:
    virtual ~CPVPManager();
//5.) Add after:
    bool            IsFighting(LPCHARACTER pkChr);
    bool            IsFighting(DWORD dwPID);