[8308] More generic code for new continent spell casting including fly form/mounts. Author: VladimirMangos

* Check new continent requirement by SPELL_ATTR_EX4_CAST_ONLY_IN_OUTLAND in
      SpellMgr::GetSpellAllowedInLocationError.
    * Also in this function let ignore any area requirement in GM-mode (except client side checks ofc if use spellbook/item)
    * For fly form/mount auras check only speciaal reqirement like special fly skill and ignore it for dead state.
    * Drop explicit fly auras drop at zone update, now this part GetSpellAllowedInLocationError functionality.
    * Allow in `spell_area` have data deepndent from ghost auras

    This all allow implement apply spells 55173/55164 to player ghost wiht DB support in `spell_area`

--HG--
branch : trunk

src/game/Player.h

@@ -2005,7 +2005,7 @@ class TRINITY_DLL_SPEC Player : public Unit
         }
         void HandleFall(MovementInfo const& movementInfo);
 
-        bool IsAllowUseFlyMountsHere() const;
+        bool IsKnowHowFlyIn(uint32 mapid, uint32 zone) const;
 
         void SetClientControl(Unit* target, uint8 allowMove);