Server/PacketIO: Update CMSG_VOID_SWAP_ITEM And Structure

To Complete Should Fix SMSG_VOID_ITEM_SWAP_RESPONSE
Server/PacketIO: Add CMSG_PET_ACTION Opcode And Structure
Merge pull request #422 from DrEhsan/master

Server/PacketIO: Update CMSG_VOID_SWAP_ITEM And Structure