sort-util: make cmp_int() generic, so that we can reuse it elsewhere

src/basic/sort-util.c

@@ -27,3 +27,7 @@ void *xbsearch_r(const void *key, const void *base, size_t nmemb, size_t size,
         }
         return NULL;
 }
+
+int cmp_int(const int *a, const int *b) {
+        return CMP(*a, *b);
+}