GL_NV_clip_space_w_scaling
http://www.opengl.org/registry/specs/NV/clip_space_w_scaling.txt
GL_NV_clip_space_w_scaling

	GL_VIEWPORT_POSITION_W_SCALE_NV 0x937C
	GL_VIEWPORT_POSITION_W_SCALE_X_COEFF_NV 0x937D
	GL_VIEWPORT_POSITION_W_SCALE_Y_COEFF_NV 0x937E
	void glViewportPositionWScaleNV (GLuint index, GLfloat xcoeff, GLfloat ycoeff)