Fixed Goliath air weapon and maxGroundHits() for siege tanks

Goliath air weapon is Hellfire_Missile_Pack (was None) with maxAirHits 2 (was 0), and siege tanks (sieged and tank mode) maxGroundHits is 1 (was 0)
Merge pull request #522 from tscmoo/dev

Fixed Goliath air weapon and maxGroundHits() for siege tanks