[unity] SkeletonGraphic now supports Unity RectMask2D. Closes #1283.

spine-unity/Assets/Spine/Runtime/spine-unity/Modules/SkeletonGraphic/Shaders/Spine-SkeletonGraphic-TintBlack.shader

@@ -111,7 +111,7 @@ Shader "Spine/SkeletonGraphic Tint Black"
 				texColor.rgb *= texColor.a;
 				#endif
 
-				texColor.a *= UnityGet2DClipping(IN.worldPosition.xy, _ClipRect);
+				texColor *= UnityGet2DClipping(IN.worldPosition.xy, _ClipRect);
 
 				#ifdef UNITY_UI_ALPHACLIP
 				clip (texColor.a - 0.001);

spine-unity/Assets/Spine/Runtime/spine-unity/Modules/SkeletonGraphic/Shaders/Spine-SkeletonGraphic.shader

@@ -109,7 +109,7 @@ Shader "Spine/SkeletonGraphic"
 
 				half4 color = (texColor + _TextureSampleAdd) * IN.color;
 
-				color.a *= UnityGet2DClipping(IN.worldPosition.xy, _ClipRect);
+				color *= UnityGet2DClipping(IN.worldPosition.xy, _ClipRect);
 
 				#ifdef UNITY_UI_ALPHACLIP
 				clip (color.a - 0.001);