AP_HAL_AVR: implement reboot in scheduler

* still need to fix system io register inits to do it like bootloader would

libraries/AP_HAL_AVR/Scheduler.cpp

@@ -1,14 +1,16 @@
 
+#include <avr/io.h>
+#include <avr/interrupt.h>
+
 #include "HAL_AVR.h"
 #include "Scheduler.h"
 using namespace AP_HAL_AVR;
 
-#include <avr/io.h>
-#include <avr/interrupt.h>
-
 #define cbi(sfr, bit) (_SFR_BYTE(sfr) &= ~_BV(bit))
 #define sbi(sfr, bit) (_SFR_BYTE(sfr) |= _BV(bit))
 
+extern const AP_HAL::HAL& hal;
+
 static volatile uint32_t timer0_overflow_count = 0;
 static volatile uint32_t timer0_millis = 0;
 static uint8_t timer0_fract = 0;
@@ -335,3 +337,19 @@ void AVRScheduler::end_atomic() {
         sei();
     }
 }
+
+void AVRScheduler::reboot() {
+    hal.uartA->println_P(PSTR("GOING DOWN FOR A REBOOT\r\n"));
+    hal.scheduler->delay(100);
+
+    cli();
+    /* Making a null pointer call will cause all AVRs to reboot
+     * but they may not come back alive properly - we need to setup
+     * the IO the way the bootloader would.
+     * pch will go back and fix this.
+     */
+    void (*fn)(void) = NULL;
+    fn();
+
+    for(;;);
+}

libraries/AP_HAL_AVR/Scheduler.h

@@ -27,6 +27,7 @@ public:
     void     resume_timer_procs();
     void     begin_atomic();
     void     end_atomic();
+    void     reboot();
 
 private:
     /* Implementation specific methods: */