Always check for X Window System, otherwise $no_x is not set to "yes"
when there is no X11. Confusing...
FPTOOLS_CHECK_LIBM()
AC_SUBST(LIBM)
-case $HostOS_CPP in
-cygwin32) ;;
-mingw32) ;;
-*) AC_PATH_XTRA() ;;
-esac
+dnl ** check for X Window System
+AC_PATH_XTRA()
dnl ** check for OpenGL/GLUT/GLX include paths and libraries
if test $GhcLibsWithHOpenGL = YES ; then