* Added basic infrastructure for visibility update in case difference player and current view point.
Just for note: seletect additional arg way beacuse repeatable search object will slow but store pointer will not safe,
so use middle case: get view point pointer early as possible at visibility updates.
* Implement dynamic object and creature activisation while it's target of far sight spell effect
* Use this for SPELL_AURA_BIND_SIGHT, SPELL_AURA_FAR_SIGHT and SPELL_EFFECT_ADD_FARSIGHT.
* Note2: some spyglass like spells let look _around_ at long distance, this hard implement in current grid loading system
Without additional changes and not implemented (you will see empty area without creatures in likes case)
* Also fixed warning spam at CMSG_MOVE_SET_CAN_FLY_ACK receive by use proper packet sructure reading.
Active objects triggrering grid loading and updating around self like players.
It can be used for event long run movements or escoring quest travels.
Also can be used for proper implementation far vision spells.
Currently only creatures can be activated by function call (from script) cr->SetActiveObjectState(true);
Please avoid lot amount active objects in same time use. Existance active objects support isn't meaning
that each rabbit must be active creature.
Also added independent grid unloading locks for explicit unloading lock,
lock for used by instance copied grids, lock counter for actiove object spawn grids locks.
Last case required for prevent double spawn active creature walk far away from spawn point.
