added mipmap gen to be compatible with versions prior gl3 that had no GL_EXT_framebuffer_object support
added mipmap gen to be compatible with versions prior gl3
that had no GL_EXT_framebuffer_object support

hach-que/SLSharp,IgniteInteractiveStudio/SLSharp,pratikv/SLSharp,pratikv/SLSharp,IgniteInteractiveStudio/SLSharp,hach-que/SLSharp