compat/regex: define out variables only used under RE_ENABLE_I18N

Wrap variables that were only used RE_ENABLE_I18N in `#ifdef
RE_ENABLE_I18N`. This eliminates compiler warnings when compiling with
NO_REGEX=YesPlease.

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

compat/regex/regex_internal.c

@@ -692,10 +692,10 @@ re_string_reconstruct (re_string_t *pstr, int idx, int eflags)
 	}
       else
 	{
+#ifdef RE_ENABLE_I18N
 	  /* No, skip all characters until IDX.  */
 	  int prev_valid_len = pstr->valid_len;
 
-#ifdef RE_ENABLE_I18N
 	  if (BE (pstr->offsets_needed, 0))
 	    {
 	      pstr->len = pstr->raw_len - idx + offset;

compat/regex/regexec.c

@@ -3059,7 +3059,9 @@ check_arrival_add_next_nodes (re_match_context_t *mctx, int str_idx,
   const re_dfa_t *const dfa = mctx->dfa;
   int result;
   int cur_idx;
+#ifdef RE_ENABLE_I18N
   reg_errcode_t err = REG_NOERROR;
+#endif
   re_node_set union_set;
   re_node_set_init_empty (&union_set);
   for (cur_idx = 0; cur_idx < cur_nodes->nelem; ++cur_idx)