Move the STM32 low power driver from core to library

To avoid further dependency issue with the core.

Signed-off-by: Frederic Pillon <frederic.pillon@st.com>

Author: fpistm

src/STM32LowPower.cpp

@@ -1,15 +1,13 @@
 /**
 ******************************************************************************
 * @file    STM32LowPower.cpp
-* @author  WI6LABS
-* @version V1.0.0
-* @date    11-December-2017
+* @author  Frederic Pillon
 * @brief   Provides a STM32 Low Power interface with Arduino
 *
 ******************************************************************************
 * @attention
 *
-* <h2><center>&copy; COPYRIGHT(c) 2017 STMicroelectronics</center></h2>
+* <h2><center>&copy; COPYRIGHT(c) 2020 STMicroelectronics</center></h2>
 *
 * Redistribution and use in source and binary forms, with or without modification,
 * are permitted provided that the following conditions are met:

src/STM32LowPower.h

@@ -1,15 +1,13 @@
 /**
 ******************************************************************************
 * @file    STM32LowPower.h
-* @author  WI6LABS
-* @version V1.0.0
-* @date    11-December-2017
+* @author  Frederic Pillon
 * @brief   Provides a STM32 Low Power interface with Arduino
 *
 ******************************************************************************
 * @attention
 *
-* <h2><center>&copy; COPYRIGHT(c) 2017 STMicroelectronics</center></h2>
+* <h2><center>&copy; COPYRIGHT(c) 2020 STMicroelectronics</center></h2>
 *
 * Redistribution and use in source and binary forms, with or without modification,
 * are permitted provided that the following conditions are met:
@@ -41,6 +39,10 @@
 
 #include <Arduino.h>
 
+#if defined(STM32_CORE_VERSION) && (STM32_CORE_VERSION  > 0x01090000)
+  #include "low_power.h"
+#endif
+
 // Check if PWR HAL enable in variants/board_name/stm32yzxx_hal_conf.h
 #ifndef HAL_PWR_MODULE_ENABLED
   #error "PWR configuration is missing. Check flag HAL_PWR_MODULE_ENABLED in variants/board_name/stm32yzxx_hal_conf.h"