remove some un-used data from b3Generic6DofConstraint

add GLRenderToTexture helper class
enable OpenGLTrueTypeFont test

btgui/OpenGLWindow/GLRenderToTexture.h

@@ -0,0 +1,28 @@
+
+#ifndef GL_RENDER_TO_TEXTURE_H
+#define GL_RENDER_TO_TEXTURE_H
+
+///See http://www.opengl-tutorial.org/intermediate-tutorials/tutorial-14-render-to-texture/
+#include "OpenGLInclude.h"
+
+struct GLRenderToTexture
+{
+	GLuint m_framebufferName;
+	GLuint	m_renderedTexture;
+	GLuint	m_depthrenderbuffer;
+	bool	m_initialized;
+public:
+		
+	GLRenderToTexture();
+	
+	void init(int width, int height);
+	bool	enable();
+	void	disable();
+	
+	virtual ~GLRenderToTexture();
+	
+};
+
+
+#endif //GL_RENDER_TO_TEXTURE_H
+