Added opcode and structure for SMSG_MOVE_ROOT/SMSG_MOVE_UNROOT.

This is sent when a player (not NPC) is rooted/unrooted. There is a 32-bit counter (m_rootCounter) that appears (based on infos founds in sniffs) to be incremented each time a Player is rooted/unrooted. 

I don't know why this value is needed, but this code appears to be working as is (I have tested it on players with various spells such as frost nova / ice block etc).