Add compatibility macros with esp8266 (#783)

cores/esp32/Arduino.h

@@ -33,6 +33,7 @@
 #include "freertos/task.h"
 #include "freertos/semphr.h"
 #include "esp32-hal.h"
+#include "esp8266-compat.h"
 #include "soc/gpio_reg.h"
 
 #include "stdlib_noniso.h"

cores/esp32/esp8266-compat.h

+// esp8266-compat.h - Compatibility functions to help ESP8266 libraries and user code run on ESP32
+
+// Copyright (c) 2017 Evandro Luis Copercini. All rights reserved.
+//
+// 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 _ESP8266_COMPAT_H_
+#define _ESP8266_COMPAT_H_
+
+#define ICACHE_FLASH_ATTR
+#define ICACHE_RAM_ATTR IRAM_ATTR
+
+
+#endif /* _ESP8266_COMPAT_H_ */
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