Fixed buffers save long strings as external.

ldump.c

@@ -126,7 +126,7 @@ static void dumpString (DumpState *D, TString *ts) {
       size_t size;
       const char *s = getlstr(ts, size);
       dumpSize(D, size + 2);
-      dumpVector(D, s, size);
+      dumpVector(D, s, size + 1);  /* include ending '\0' */
       D->nstr++;  /* one more saved string */
       setsvalue(D->L, &key, ts);  /* the string is the key */
       setivalue(&value, D->nstr);  /* its index is the value */