AP_HAL_AVR: header include fixups

libraries/AP_HAL_AVR/PWMOutput.h

@@ -3,6 +3,7 @@
 #define __AP_HAL_AVR_PWM_OUTPUT_H__
 
 #include <AP_HAL.h>
+#include "AP_HAL_AVR_Namespace.h"
 
 class AP_HAL_AVR::APM1PWMOutput : public AP_HAL::PWMOutput {
 public:

libraries/AP_HAL_AVR/SPIDriver.h

@@ -3,6 +3,7 @@
 #define __AP_HAL_ARDUINO_SPI_DRIVER_H__
 
 #include <AP_HAL.h>
+#include "AP_HAL_AVR_Namespace.h"
 
 class AP_HAL_AVR::ArduinoSPIDriver : public AP_HAL::SPIDriver {
 public:

libraries/AP_HAL_AVR/Storage.h

@@ -4,6 +4,7 @@
 #define __AP_HAL_AVR_STORAGE_H__
 
 #include <AP_HAL.h>
+#include "AP_HAL_AVR_Namespace.h"
 
 class AP_HAL_AVR::AVREEPROMStorage : public AP_HAL::Storage {
 public:

libraries/AP_HAL_AVR/UARTDriver.h

@@ -3,6 +3,9 @@
 #define __AP_HAL_AVR_UART_DRIVER_H__
 
 #include <stdint.h>
+#include <stdarg.h>
+
+#include <avr/interrupt.h>
 
 #include <AP_Common.h>
 #include <AP_HAL.h>