[unity] Fixed compile error on Unity 2017.1 of last commit. See #1640.

spine-unity/Assets/Spine/Editor/spine-unity/Editor/Components/SkeletonGraphicInspector.cs

@@ -35,6 +35,10 @@
 #define HAS_CULL_TRANSPARENT_MESH
 #endif
 
+#if UNITY_2017_2_OR_NEWER
+#define NEWPLAYMODECALLBACKS
+#endif
+
 using System.Reflection;
 using UnityEditor;
 using UnityEngine;
@@ -142,15 +146,27 @@ namespace Spine.Unity.Editor {
 			separatorSlotNames = so.FindProperty("separatorSlotNames");
 			separatorSlotNames.isExpanded = true;
 
+#if NEWPLAYMODECALLBACKS
 			EditorApplication.playModeStateChanged += OnPlaymodeChanged;
+#else
+			EditorApplication.playmodeStateChanged += OnPlaymodeChanged;
+#endif
 		}
 
 		void OnDisable () {
+#if NEWPLAYMODECALLBACKS
 			EditorApplication.playModeStateChanged -= OnPlaymodeChanged;
+#else
+			EditorApplication.playmodeStateChanged -= OnPlaymodeChanged;
+#endif
 			DisableEditReferenceRectMode();
 		}
 
+#if NEWPLAYMODECALLBACKS
 		void OnPlaymodeChanged (PlayModeStateChange mode) {
+#else
+		void OnPlaymodeChanged () {
+#endif
 			DisableEditReferenceRectMode();
 		}