Merge branch 'master' of https://github.com/leibin2014/mbed into leibin2014-master

Conflicts:
	libraries/mbed/targets/cmsis/TARGET_STM/TARGET_STM32F0/TARGET_NUCLEO_F072RB/system_stm32f0xx.c

Author: 0xc0170

libraries/mbed/targets/cmsis/TARGET_STM/TARGET_STM32F0/TARGET_NUCLEO_F072RB/system_stm32f0xx.c

@@ -444,7 +444,7 @@ uint8_t SetSysClock_PLL_HSI(void)
   RCC_OscInitStruct.LSIState                = RCC_LSI_OFF;
   RCC_OscInitStruct.PLL.PLLState            = RCC_PLL_ON;
   RCC_OscInitStruct.PLL.PLLSource           = RCC_PLLSOURCE_HSI; // HSI div 2
-  RCC_OscInitStruct.PLL.PREDIV              = RCC_PREDIV_DIV1;
+  RCC_OscInitStruct.PLL.PREDIV              = RCC_PREDIV_DIV2;
   RCC_OscInitStruct.PLL.PLLMUL              = RCC_PLL_MUL12;
   if (HAL_RCC_OscConfig(&RCC_OscInitStruct) != HAL_OK) {
       return 0; // FAIL