test-calc-23889: Skip test on 32-bit platforms

This test fails on some 32-bit platforms as mentioned in
https://lists.gnu.org/archive/html/emacs-devel/2017-05/msg00737.html
* test/lisp/calc/calc-tests.el (test-calc-23889): Skip when
the Lisp integer is not big enough.

test/lisp/calc/calc-tests.el

@@ -88,6 +88,7 @@ An existing calc stack is reused, otherwise a new one is created."
 
 (ert-deftest test-calc-23889 ()
   "Test for http://debbugs.gnu.org/23889 and 25652."
+  (skip-unless (>= math-bignum-digit-length 9))
   (dolist (mode '(deg rad))
     (let ((calc-angle-mode mode))
       ;; If user inputs angle units, then should ignore `calc-angle-mode'.