v0.4.2: Game logic now occurs in a separate thread

This is going to cause a LOT of bugs, next several commits will likely be fixing them.

core/src/main/java/com/shatteredpixel/shatteredpixeldungeon/actors/Actor.java

@@ -164,6 +164,10 @@ public abstract class Actor implements Bundlable {
 			current = null;
 		}
 	}
+
+	public static boolean processing(){
+		return current != null;
+	}
 	
 	public static void process() {
 		
@@ -191,7 +195,8 @@ public abstract class Actor implements Bundlable {
 
 			if  (current != null) {
 
-				if (current instanceof Char && ((Char)current).sprite.isMoving) {
+				if (current instanceof Char &&
+						((Char) current).sprite != null && ((Char)current).sprite.isMoving) {
 					// If it's character's turn to act, but its sprite
 					// is moving, wait till the movement is over
 					current = null;

core/src/main/java/com/shatteredpixel/shatteredpixeldungeon/scenes/GameScene.java

@@ -400,6 +400,8 @@ public class GameScene extends PixelScene {
 		}
 	}
 
+	private Thread t;
+
 	@Override
 	public synchronized void update() {
 		if (Dungeon.hero == null || scene == null) {
@@ -410,7 +412,17 @@ public class GameScene extends PixelScene {
 		
 		if (!freezeEmitters) water.offset( 0, -5 * Game.elapsed );
 
-		Actor.process();
+		if (!Actor.processing() && (t == null || !t.isAlive())) {
+			t = new Thread() {
+				@Override
+				public void run() {
+					Actor.process();
+				}
+			};
+			//if cpu time is limited, game should prefer drawing the current frame
+			t.setPriority(Thread.MIN_PRIORITY);
+			t.start();
+		}
 		
 		if (Dungeon.hero.ready && Dungeon.hero.paralysed == 0) {
 			log.newLine();