Core/Warden: Fix crash

https://github.com/TrinityCore/TrinityCore/commit/12cafcf96b3def0117baa1b67725d7981c729d1f
Scripts/Eastern Plaguelands: Fix flypath exploit

Fix npc id 17209 in Eastern Plaguelands enabling taxi cheat to players just by talking to it.

https://github.com/TrinityCore/TrinityCore/commit/aaa4b3a1240b7b25a4050a7c6d3dc5184f3e581d
Core/Spells: Possible crash fix

Get Unit target with the proper method instead of retrieving Object target and then casting it to Unit, possible dereferencing NULL.

https://github.com/TrinityCore/TrinityCore/commit/84e73448f2467e733f6037f795e26f49997d3cd1
Core: Add rest of checks from SendListInventory to BuyItemFromVendorSlot.

https://github.com/TrinityCore/TrinityCore/commit/49593361e3b4296e4275467dbe8480842cc3a8ab
Core: Add rest of checks from SendListInventory to BuyItemFromVendorSlot && Rename isGameMaster() too IsGameMaster.