Replace SIMULATOR with __AVR__ in several places.

Previously some features were excluded based on whether SIMULATOR
was defined. But in fact these should have been included when __AVR__
was defined. These used to be the same thing, but now with ARM coming
into the picture, they are not. Fix the situation so AVR includes are
truly only used when __AVR__ is defined.

The _crc16_update function appears to be specific to AVR; I've kept the
alternate implementation limited to AVR in that case in crc.c. I think
this is the right thing to do, but I am not sure. Maybe ARM has some
equivalent function in their libraries.

crc.c

@@ -4,7 +4,7 @@
 	\brief crc16 routine
 */
 
-#ifndef SIMULATOR
+#ifdef __AVR__
 #include	<util/crc16.h>
 #else
 

dda.c

@@ -7,7 +7,7 @@
 #include	<string.h>
 #include	<stdlib.h>
 #include	<math.h>
-#ifndef SIMULATOR
+#ifdef __AVR__
 #include	<avr/interrupt.h>
 #endif
 

dda_lookahead.c

@@ -11,7 +11,7 @@
 #include <stdlib.h>
 #include <stddef.h>
 #include <math.h>
-#ifndef SIMULATOR
+#ifdef __AVR__
 #include <avr/interrupt.h>
 #endif
 

dda_queue.c

@@ -5,7 +5,7 @@
 */
 
 #include	<string.h>
-#ifndef SIMULATOR
+#ifdef __AVR__
 #include	<avr/interrupt.h>
 #endif
 

gcode_process.c

@@ -5,7 +5,7 @@
 */
 
 #include	<string.h>
-#ifndef SIMULATOR
+#ifdef __AVR__
 #include	<avr/interrupt.h>
 #endif
 

intercom.c

@@ -4,7 +4,7 @@
 	\brief motherboard <-> extruder board protocol
 */
 
-#ifndef SIMULATOR
+#ifdef __AVR__
 #include	<avr/io.h>
 #include	<avr/interrupt.h>
 #endif

memory_barrier.h

@@ -13,7 +13,7 @@
                          if (save_reg) sei(); \
                        }
 
-#else
+#elif defined __AVR__
 #include <util/atomic.h>
 #include <avr/version.h>
 

temp.c

@@ -10,7 +10,7 @@
 */
 
 #include	<stdlib.h>
-#ifndef SIMULATOR
+#ifdef __AVR__
 #include	<avr/eeprom.h>
 #include	<avr/pgmspace.h>
 #endif

timer.c

@@ -10,7 +10,7 @@
 	Teacup has tried numerous timer management methods, and this is the best so far.
 */
 
-#ifndef SIMULATOR
+#ifdef __AVR__
 #include	<avr/interrupt.h>
 #endif
 #include	"memory_barrier.h"

timer.h

@@ -2,7 +2,7 @@
 #define	_TIMER_H
 
 #include	<stdint.h>
-#ifndef SIMULATOR
+#ifdef __AVR__
 #include	<avr/io.h>
 #endif
 #include "simulator.h"