[XForms] missing #include in glcanvas.h

[Rouben Rostamian]

Minor bug in xforms-1.0.90:

Where:
    xforms-1.0.90/gl/glcanvas.h

Problem:
   Missing header:
        #include <GL/glx.h>

How to fix:
   Add:
        #include <GL/glx.h>
   near the top of xforms-1.0.90/gl/glcanvas.h

Details:

The #include <GL/glx.h> is needed to resolve references to
GLXContext in xforms-1.0.90/gl/glcanvas.h.

Currently, the supplied demos work by accident, because they happen
to #include the header files

   #include <GL/glx.h>
   #include <glcanvas.h>

just in the right order.  Reversing the #include order will break them.

-- 
Rouben Rostamian