Stuff

    AC_TRY_RUN([
#include <X11/Xlib.h>
main() {
    XPoint pt;
    pt.x = pt.y = 0;
    return pt.x;
}
    ],[x11_works=yes])
    AC_MSG_RESULT($x11_works)
    if test "x$x11_works" = "xyes" ; then
        LDFLAGS="$LDFLAGS $X_LIBS"
        AC_MSG_CHECKING(for X11 link functionality)
        AC_TRY_RUN([
#include <X11/Xlib.h>
main() {
    XModifierKeymap *xmkm;
    xmkm=XNewModifiermap(1);
    return xmkm==NULL;
}
        ],[x11_works=yes])
        AC_MSG_RESULT($x11_works)
    fi