Fix off-by-one error when initializing vectors in `make-srfi-4-vector'.

* libguile/srfi-4.c (scm_make_srfi_4_vector): When FILL is bound and
  non-zero, initialize the last element.

* test-suite/tests/srfi-4.test ("TAG vectors")["make-TAGvector"]: New
  tests.

libguile/srfi-4.c

@@ -267,9 +267,15 @@ SCM_DEFINE (scm_make_srfi_4_vector, "make-srfi-4-vector", 2, 1, 0,
             scm_t_array_handle h;
             size_t len;
             ssize_t pos, inc;
+
             scm_uniform_vector_writable_elements (ret, &h, &len, &inc);
+
             for (pos = 0; pos != h.dims[0].ubnd; pos += inc)
               scm_array_handle_set (&h, pos, fill);
+
+	    /* Initialize the last element.  */
+	    scm_array_handle_set (&h, pos, fill);
+
             scm_array_handle_release (&h);
           }
         return ret;