Module tests

[Eli Zaretskii]

Commit 2b3f5de2b3 removed these 2 tests:

  (should (= (mod-test-sum 1 #x1fffffff)
             (1+  #x1fffffff)))
  (should (= (mod-test-sum -1 #x20000000)
             #x1fffffff))

They were written to test the code in emacs-module.c which switches
from scalar values to cons cells when the integer value is too large
for 32 bits and Emacs is compiled with wide ints.

I don't understand why the removal.  AFAICS, we still switch from
integers to cons cells, so the borderline values just above and below
the threshold are where be dragons, and we should keep them (they
helped me to find and fix a couple of bugs in the previous
implementation).  What am I missing?