If SAL_WARN() does nothing, no point in CHECK_GL_ERROR() either

Earlier, CHECK_GL_ERROR() always called OpenGLHelper::checkGLError().
That function looks up the OpenGL error status using glGetError(),
which might be a not so light-weight operation, and outputs error
information using SAL_WARN(). In a production build where SAL_WARN()
is a no-op anyway, that is fairly pointless.

Change-Id: I2d044bff6128a8ac7739020f8e414d7d3615e8d5

include/vcl/opengl/OpenGLHelper.hxx

@@ -99,7 +99,11 @@ public:
 #endif
 };
 
+#ifdef SAL_LOG_WARN
 #define CHECK_GL_ERROR() OpenGLHelper::checkGLError(__FILE__, __LINE__)
+#else
+#define CHECK_GL_ERROR() do { } while (false)
+#endif
 
 #endif