[Core] Fix some warnings reported by static analysis
Credits to stfx [c12729]
[Core] Fix warning reported by travis ;)
Credits to stfx [c12730]
[Core] Implement TARGET_RANDOM_UNIT_CHAIN_IN_AREA
Also unify the TARGET_RANDOM_CHAIN_IN_AREA code
Credits to @boxa and @xfurry [c12732]
[Core] Implement TARGET_FRIENDLY_FRONTAL_CONE
Credit to @boxa and @xfurry [c12733]
[Core] Implement basic support for area 284 - Trigger Linked Aura
Notes: there are various cases that are not yet implemented, such as
Gear Scaling or Death Knight spells
Credits to @xfurry [c12734]