Core: Fix build

(cherry picked from commit 81daef8b2205fca4310720d3186bafca8d75a792)
Scripts/Pet: Fix non pch compile
DB/EAI: Fix unit_field changes, outdated since initial 3.x versions
Scripted: Use now override for instance scripts
Merge branch 'master' of github.com:TrinityCore/TrinityCore into 4.3.4

Conflicts:
	src/server/scripts/EasternKingdoms/ZulAman/instance_zulaman.cpp
	src/server/scripts/EasternKingdoms/ZulGurub/instance_zulgurub.cpp
	src/server/scripts/Northrend/Nexus/EyeOfEternity/boss_malygos.cpp