Improve GL debug (#626)

vtm-playground/src/org/oscim/test/renderer/CustomRenderer.java

@@ -120,7 +120,7 @@ public class CustomRenderer extends LayerRenderer {
         // Draw the triangle
         gl.drawArrays(GL.TRIANGLE_STRIP, 0, 4);
 
-        GLUtils.checkGlError("...");
+        GLUtils.checkGlError(getClass().getName() + ": render() end");
     }
 
     private boolean init() {

vtm-playground/src/org/oscim/test/renderer/HexagonRenderTest.java

@@ -175,7 +175,7 @@ public class HexagonRenderTest extends GdxMapApp {
                 }
             }
 
-            GLUtils.checkGlError("...");
+            GLUtils.checkGlError(getClass().getName() + ": render() end");
         }
 
         private boolean init() {