ZC_Skill_Melee_Ground and SkillHitInfo

[Terotrous]

For Behead, and maybe other skills, Zenmya reveals that the official sends skillhitinfo along with the ZC_Skill_Melee_Ground packet, though in our implementations we typically send no hitinfo with it and instead send it later in a ZC_Skill_Hit_Info packet. ZC_Skill_Melee_Ground also has the effect of playing the skill's animation on the client side.

In Behead's specific case, it has 2 hitboxes, the first of which uses the ZC_Skill_Melee_Ground packet, and the second creates a ZC_Skill_Hit_Info packet. Currently it sends two ZC_Skill_Hit_Info packets, which is visually indistinguishable in gameplay, but may indicate that our implementation of the skill packets could be wrong / innaccurate.