IO and OpenGL on Linux (glClearColor not found)

Hi,

I'm trying to compile IO and run Flux examples on linux, but I have a few
problems:

 -  First (from git), the addons/CMakeLists.txt disabled the cairo addon
necessary to run Flux. I had to reactivate it manually. Is that normal?
 -  Then, I'm getting the following error when running Flux examples:

  Exception: Color does not respond to 'glClearColor'
  ---------
  Color glClearColor                   OSWindow.io 208
  OSWindow drawBackground              OSWindow.io 200
  OSWindow display                     Application.io 106
  Application display                  [GLUT] 0
  Application run                      main.io 28
  CLI doFile                           Z_CLI.io 140
  CLI run                              IoState_runCLI() 1

(running /usr/local/lib/io/addons/Flux/samples/FileBrowser/main.io)

Do you have an idea why I don't have glClearColor on my system?
Thanks,

Mildred