don't use GL_LINEAR_MIPMAP_LINEAR for shadow maps

optimize gpu upload (use glBufferSubData instead of glMapBuffer
Avoid checking char array against zero.

examples/OpenGLWindow/SimpleOpenGL3App.cpp

@@ -173,6 +173,7 @@ SimpleOpenGL3App::SimpleOpenGL3App(	const char* title, int width,int height, boo
     b3Assert(glGetError() ==GL_NO_ERROR);
 
 	m_instancingRenderer = new GLInstancingRenderer(128*1024,128*1024*1024);
+
     m_primRenderer = new GLPrimitiveRenderer(width,height);
     
     m_renderer = m_instancingRenderer ;