Patch: Fix configure check for Xaw3d

[Stephen J. Turnbull]

Mike FABIAN writes:

 >          dnl Must not be a 3d library...
 > -        AC_CHECK_LIB($athena_variant, threeDClassRec,
 > +        AC_CHECK_LIB($athena_variant, XawSme3dComputeTopShadowRGB,

What is this supposed to fix?