Pacify MSVC warnings for random.c

mrbgems/mruby-random/src/random.c

@@ -44,7 +44,7 @@ static mrb_value
 mrb_random_mt_srand(mrb_state *mrb, mt_state *t, mrb_value seed)
 {
   if (mrb_nil_p(seed)) {
-    seed = mrb_fixnum_value(time(NULL) + mt_rand(t));
+    seed = mrb_fixnum_value((mrb_int)(time(NULL) + mt_rand(t)));
     if (mrb_fixnum(seed) < 0) {
       seed = mrb_fixnum_value( 0 - mrb_fixnum(seed));
     }