glXBindTexImageEXT

Hello,
I am trying to bind an X11 pixmap obtained from the XComposite Extension 
to an OpenGL texture. GLX is supposed to have an extension for doing 
this very thing as mentioned here [1]. Following this tutorial, I have 
written a program which uses the glXBindTexImageEXT found in glx.h.

When I try to compile my program, it is telling me that 
glXBindTexImageEXT and glXReleaseTexImageEXT are implicitly declared. I 
guessed that it was being #ifndef out but I couldn't find where. I am 
using ArchLinux with the mesa-git package so I am using the git version. 
The glx.h file is owned by the mesa-git package and so this is why I am 
sending this e-mail to this list.

Is there a newer function I should be using to bind a pixmap to a 
texture or should I copy pixel data myself (would be nice to copy it 
directly on the video card)?

Thank you for your time,
Emmanuel

[1]http://www.opengl.org/registry/specs/EXT/texture_from_pixmap.txt