GL_EXT_texture_env
http://oss.sgi.com/projects/ogl-sample/registry/EXT/texture_env.txt
	GL_TEXTURE_ENV0_EXT 0
	GL_TEXTURE_ENV_SHIFT_EXT 0
	GL_ENV_BLEND_EXT 0
	GL_ENV_ADD_EXT 0
	GL_ENV_REPLACE_EXT 0
	GL_ENV_SUBTRACT_EXT 0
	GL_TEXTURE_ENV_MODE_ALPHA_EXT 0
	GL_ENV_REVERSE_BLEND_EXT 0
	GL_ENV_REVERSE_SUBTRACT_EXT 0
	GL_ENV_COPY_EXT 0
	GL_ENV_MODULATE_EXT 0