Add test for "no endstops defined" build

This configuration used to fail.  Now it's fixed.  Test the
configuration to ensure it doesn't break again in the future.

Makefile-common

@@ -135,6 +135,9 @@ regressiontests:
 	# Continue with ARM based boards, a Gen7-ARM.
 	$(MAKE) -f Makefile-ARM USER_CONFIG=testcases/config.regtest-gen7-arm.h \
 	  EXTRA_CFLAGS=-Werror all
+	# Config scenario: no endstops defined
+	$(MAKE) -f Makefile-AVR USER_CONFIG=testcases/config.regtest-no-endstops.h \
+	  MCU=atmega644 F_CPU=20000000UL EXTRA_CFLAGS=-Werror all
 	# Don't forget the hostside simulator.
 	$(MAKE) -f Makefile-SIM USER_CONFIG=testcases/config.regtest-gen7-avr.h \
 	  EXTRA_CFLAGS=-Werror all

testcases/board.regtest-no-endstops.h

@@ -0,0 +1,75 @@
+/* Test: Does the code still compile without endstops?
+ *
+ * This config file is defined to test this, at least on
+ * one processor.
+ */
+#define CPU                      atmega644
+#ifndef F_CPU
+#define F_CPU                    20000000UL
+#endif
+#define MOTHERBOARD
+
+//#define TX_ENABLE_PIN            xxxx
+//#define RX_ENABLE_PIN            xxxx
+
+#define X_STEP_PIN               DIO19
+#define X_DIR_PIN                DIO18
+//#define X_MIN_PIN                DIO7
+//#define X_MAX_PIN                DIO6
+//#define X_ENABLE_PIN             xxxx
+//#define X_INVERT_DIR
+//#define X_INVERT_MIN
+//#define X_INVERT_MAX
+//#define X_INVERT_ENABLE
+
+#define Y_STEP_PIN               DIO23
+#define Y_DIR_PIN                DIO22
+//#define Y_MIN_PIN                DIO5
+//#define Y_MAX_PIN                DIO2
+//#define Y_ENABLE_PIN             xxxx
+//#define Y_INVERT_DIR
+//#define Y_INVERT_MIN
+//#define Y_INVERT_MAX
+//#define Y_INVERT_ENABLE
+
+#define Z_STEP_PIN               DIO26
+#define Z_DIR_PIN                DIO25
+//#define Z_MIN_PIN                DIO1
+//#define Z_MAX_PIN                DIO0
+//#define Z_ENABLE_PIN             xxxx
+//#define Z_INVERT_DIR
+//#define Z_INVERT_MIN
+//#define Z_INVERT_MAX
+//#define Z_INVERT_ENABLE
+
+#define E_STEP_PIN               DIO28
+#define E_DIR_PIN                DIO27
+//#define E_ENABLE_PIN             xxxx
+//#define E_INVERT_DIR
+//#define E_INVERT_ENABLE
+
+#define PS_ON_PIN                DIO15
+//#define PS_MOSFET_PIN            xxxx
+#define STEPPER_ENABLE_PIN       DIO24
+#define STEPPER_INVERT_ENABLE
+
+#define SD_CARD_SELECT_PIN       DIO10
+
+#ifndef DEFINE_TEMP_SENSOR
+  #define DEFINE_TEMP_SENSOR(...)
+#endif
+
+#define TEMP_THERMISTOR
+DEFINE_TEMP_SENSOR(extruder, TT_THERMISTOR, AIO1,  THERMISTOR_EXTRUDER)
+DEFINE_TEMP_SENSOR(bed,      TT_THERMISTOR, AIO2,  THERMISTOR_BED)
+
+#ifndef DEFINE_HEATER
+  #define DEFINE_HEATER(...)
+#endif
+
+DEFINE_HEATER(extruder, DIO4,    0,      1)
+DEFINE_HEATER(bed,      DIO3,    0,      1)
+
+#define HEATER_EXTRUDER HEATER_extruder
+#define HEATER_BED HEATER_bed
+#define BAUD                     115200

testcases/config.regtest-no-endstops.h

@@ -0,0 +1,6 @@
+
+// Configuration for controller board.
+#include "board.regtest-no-endstops.h"
+
+// Configuration for printer
+#include "../config/printer.wolfstrap.h"