Offset integer ranges in runtime block data serialization

this is useful for stuff like snow layers where the range doesn't start at 0.

src/block/FrostedIce.php

@@ -40,7 +40,7 @@ class FrostedIce extends Ice{
 	}
 
 	protected function encodeState(RuntimeDataWriter $w) : void{
-		$w->writeInt(2, $this->age);
+		$w->writeBoundedInt(2, 0, self::MAX_AGE, $this->age);
 	}
 
 	public function getAge() : int{ return $this->age; }