Marks target object as dirty.

Unity internally uses the dirty flag to find out when assets have changed and need to be saved to disk.

E.g. if you modify a prefab's MonoBehaviour or ScriptableObject variables, you must tell Unity that the value has changed. Unity builtin components internally call SetDirty whenever a property changes. MonoBehaviour or ScriptableObject don't do this automatically so if you want your value to be saved you need to call SetDirty.

	#pragma strict
	// This example shows a custom inspector for an
	// object "MyPlayerEditor", which has two variables, speed and ammo.
	@CustomEditor(MyPlayer)
	class MyPlayerEditor extends Editor {
		function OnInspectorGUI()
		{
			var targetPlayer = target as MyPlayer;
			EditorGUILayout.LabelField ("Some help", "Some other text");
			GUI.changed = false;
			targetPlayer.speed = EditorGUILayout.Slider ("Speed", targetPlayer.speed, 0, 100);
			if (GUI.changed)
				EditorUtility.SetDirty(targetPlayer);
		}
	}