Fix typo in cortex_handlers.

Fix #149

Author: cmaglie

cores/arduino/cortex_handlers.c

@@ -36,7 +36,7 @@ void Dummy_Handler(void)
 
 /* Cortex-M0+ core handlers */
 void HardFault_Handler(void) __attribute__ ((weak, alias("Dummy_Handler")));
-void Reest_Handler    (void);
+void Reset_Handler    (void);
 void NMI_Handler      (void) __attribute__ ((weak, alias("Dummy_Handler")));
 void SVC_Handler      (void) __attribute__ ((weak, alias("Dummy_Handler")));
 void PendSV_Handler   (void) __attribute__ ((weak, alias("Dummy_Handler")));