Improve TWOPASS model detection & fix alphatest SSAO pass
* Alpha-tested materials are now considered opaque
Alpha test HL2 door props with windows in it
(Sub)Material overrides affect depth passes
* So making a glass prop (or glass part of a prop) opaque actually affects the flashlight shadow
Combine Mine relationship adjustments
* Doesn't attack Combine Gunship, Manhacks, Stalkers
* Always attacks barnacles
* Respects IgnorePlayer and DisableAI settings
Delete clientside part of prop_vehicle_cannon
* Serverside part was already removed from GMod
* Also removes it from the FGD
Apply same restrictions on APC as the Jeep has (properties & PhysGun)
Fixed client D.O.G. ragdolls leaving behind ropes on removal