What is your dglOpenGL version? I find something you describe at line 15021:
Code:
    {$IFDEF DGL_LINUX}
      // GLX_VERSION_1_4 (needs to be first)
      glXGetProcAddress := dglGetProcAddress('glXGetProcAddress', nil, True);
So it seems to have gone through big changes. My header is not propably latest either, Version 4.4 date 2013/07/22.