Add opcode CMSG_SET_ACTION_BUTTON
Update structure HandleSetActionButtonOpcode
Merge pull request #257 from projectcore/patch-37

Update structure HandleSetActionButtonOpcode
Merge pull request #256 from projectcore/patch-36

Add opcode CMSG_SET_ACTION_BUTTON
Core/PacketIO: Updated SMSG_TRAINER_LIST structure and opcode.
Updated CMSG_TRAINER_LIST structure and opcode.
Updated CMSG_TRAINER_BUY_SPELL structure and opcode.
Updated SMSG_LEARNED_SPELL structure and opcode.