Move panic handler and gdbstub into esp32 component, clean up wdt according to merge req suggestions

components/esp32/include/esp_gdbstub.h

@@ -0,0 +1,22 @@
+// Copyright 2015-2016 Espressif Systems (Shanghai) PTE LTD
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+#ifndef GDBSTUB_H
+#define GDBSTUB_H
+
+#include <xtensa/config/core.h>
+#include "freertos/xtensa_api.h"
+
+void esp_gdbstub_panic_handler(XtExcFrame *frame);
+
+#endif