Avoid use internal core header file use Arduino.h instead

Up to the used core to define properly what the library need.
Mainly the cortex M core to use:
Ex: for STM32F103 based board:
#define __CORTEX_M (0x03U) /*!< Cortex-M Core */

https://github.com/stm32duino/Arduino_Core_STM32 uses the CMSIS which defined it.
https://github.com/ARM-software/CMSIS/blob/6891719834ac6ca2a79e8ded00620faffae10ae8/CMSIS/Include/core_cm3.h#L79

Fix #3

Signed-off-by: Frederic Pillon <[email protected]>

Author: fpistm

src/port.c

@@ -3,7 +3,7 @@
  * @author  Frederic Pillon <[email protected]> for STMicroelectronics.
  * @brief   Include source of FreeRTOS portable layer file to match Arduino library format
  */
-#include "stm32_def.h"
+#include <Arduino.h>
 
 #ifndef __CORTEX_M
 #pragma GCC error  "no \"__CORTEX_M\" definition"

src/portmacro.h

@@ -6,7 +6,7 @@
 
 #ifndef _PORTMACRO_H_
 #define _PORTMACRO_H_
-#include "stm32_def.h"
+#include <Arduino.h>
 
 #ifndef __CORTEX_M
 #pragma GCC error  "no \"__CORTEX_M\" definition"