ImpactSound for Longbow's HellfireAA.

In addition, I noticed a missing .aud extension and fixed that as well.
Merge pull request #3661 from reaperrr/sound-fix

Minor sound fixes
Increases contrast between main snow color and darker patches of snow, additionally gives the darker patches a slightly more blueish color.
Merge pull request #3663 from reaperrr/cnc-snow-color-fix

C&C mod snow brightness fix
Merge pull request #3668 from pchote/more-polish

Polish fixes for muzzle flashes and cash ticks.
Merge pull request #3665 from pchote/frozen-fog-prereqs

Rework bibs (again).
Add Order.ExtraData field.
Add ITargetableInfo interface for querying target types.
Change WeaponInfo.EffectivenessAgainst to take ActorInfo.
Introduce Target.Type property.
Merge IOrderTargeter.CanTargetActor and CanTargetLocation.
Allow world and (render-) player actors to render.
Use selection priority when picking tooltip actor.
Track per-player frozen actors.
Show tooltips for frozen actors.
Add FrozenActor target type.
Add plumbing for issuing orders against frozen actors.
Add helper for resolving orders against frozen actors.
Enable frozen order: Attack.
Enable frozen order: DeliverSupplies.