Once upon a time, this was used to extract prototypes from the shader
containing GLSL built-in functions. This was removed by f5692f45 in
November 2010 for Mesa 7.10.
Signed-off-by: Ian Romanick <ian.d.romanick@intel.com>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Eric Engestrom <eric@engestrom.ch>