GL_OES_single_precision
http://oss.sgi.com/projects/ogl-sample/registry/OES/single_precision.txt
	void glClearDepthfOES (GLclampd depth)
	void glClipPlanefOES (GLenum plane, const GLfloat* equation)
	void glDepthRangefOES (GLclampf n, GLclampf f)
	void glFrustumfOES (GLfloat l, GLfloat r, GLfloat b, GLfloat t, GLfloat n, GLfloat f)
	void glGetClipPlanefOES (GLenum plane, GLfloat* equation)
	void glOrthofOES (GLfloat l, GLfloat r, GLfloat b, GLfloat t, GLfloat n, GLfloat f)