Modem: Respond to % escaped commands, fixes Windows autodetection taking a long time

src/network/net_modem.c

@@ -1091,6 +1091,10 @@ modem_do_command(modem_t *modem, int repeat)
                     }
                     break;
                 }
+            case '%': // % escaped commands
+                // Windows 98 modem prober sends unknown command AT%V
+                modem_send_res(modem, ResERROR);
+                return;
             case '\0':
                 modem_send_res(modem, ResOK);
                 return;