Reuse `natstr` if it equals `endstr`

pack.c

@@ -36,10 +36,11 @@
  */
 #ifdef HAVE_TRUE_LONG_LONG
 static const char natstr[] = "sSiIlLqQjJ";
+# define endstr natstr
 #else
 static const char natstr[] = "sSiIlLjJ";
-#endif
 static const char endstr[] = "sSiIlLqQjJ";
+#endif
 
 #ifdef HAVE_TRUE_LONG_LONG
 /* It is intentional to use long long instead of LONG_LONG. */