improved siegetank weapon vs. heavy armor & buildings

This will make it slightly more relevant on the battlefield. It shouldn't be excellent at fighting armor, since armor is what should kill it, but it shouldn't be totally helpless either.

damage vs. heavy increased 25% -> 50%
damage vs. wood increased 60% -> 80%
inaccuracy reduced 45 -> 40
speed increased ever so slightly.

mods/d2k/weapons.yaml

@@ -376,19 +376,19 @@ FakeMissile:
 	MinRange: 2
 	Report: MORTAR1
 	Projectile: Bullet
-		Speed: 18
+		Speed: 20
 		High: true
 		Shadow: yes
 		Angle: .1
-		Inaccuracy: 45
+		Inaccuracy: 40
 		ContrailLength: 20
 	Warhead:
 		Spread: 12
 		Versus: 
 			None: 100%
-			Wood: 60%
+			Wood: 80%
 			Light: 50%
-			Heavy: 25%
+			Heavy: 50%
 			Concrete: 80%
 		Explosion: large_explosion
 		WaterExplosion: large_splash