use thread_local for ntoa buf

*** 1219,1228 ****
--- 1219,1232 ----
                                  }
                                  if (strncmp(arg, "-xc99=%none", 11) == 0) {
                                          newae(ctx->i_ae, "-std=gnu89");
                                          break;
                                  }
+                                 if (strncmp(arg, "-xc11=%all", 10) == 0) {
+                                         newae(ctx->i_ae, "-std=gnu11");
+                                         break;
+                                 }
                                  if (strncmp(arg, "-xchip=", 7) == 0) {
                                          xlate(ctx->i_ae, arg + 7, xchip_tbl);
                                          break;
                                  }
                                  if (strncmp(arg, "-xcode=", 7) == 0) {