Added error checking in initialization of GLEW

src/SFML/Graphics/GLCheck.cpp

@@ -112,9 +112,16 @@ void EnsureGlewInit()
     static bool initialized = false;
     if (!initialized)
     {
-        glewInit();
+        GLenum status = glewInit();
+        if (status == GLEW_OK)
+        {
             initialized = true;
         }
+        else
+        {
+            Err() << "Failed to initialize GLEW, " << glewGetErrorString(status) << std::endl;
+        }
+    }
 }
 
 } // namespace priv