Fix issue with stricter C++ compiler with atomic definition.

(It still feels strange to not be able to store 0 in an atomic unsigned long).

m-genint.h

@@ -67,7 +67,7 @@ static inline void genint_init(genint_t s, size_t n)
     return;
   }
   for(size_t i = 0; i < alloc; i++)
-    atomic_init(&s->data[i], 0);
+    atomic_init(&s->data[i], 0UL);
   GENINT_CONTRACT(s);
 }