Add COUNT macro and apply

Marlin/Marlin_main.cpp

     if (code_seen('P') && pin_status >= 0 && pin_status <= 255)
       pin_number = code_value_short();
 
-    for (int8_t i = 0; i < (int8_t)(sizeof(sensitive_pins) / sizeof(*sensitive_pins)); i++) {
+    for (int8_t i = 0; i < COUNT(sensitive_pins); i++) {
       if (sensitive_pins[i] == pin_number) {
         pin_number = -1;
         break;
 
     if (pin_state >= -1 && pin_state <= 1) {
 
-      for (int8_t i = 0; i < (int8_t)(sizeof(sensitive_pins)/sizeof(*sensitive_pins)); i++) {
+      for (int8_t i = 0; i < COUNT(sensitive_pins); i++) {
         if (sensitive_pins[i] == pin_number) {
           pin_number = -1;
           break;

Marlin/Sd2PinMap.h

  */
 // Warning this file was generated by a program.
 #include "Marlin.h"
+#include "macros.h"
+
 #ifdef SDSUPPORT
 
 #ifndef Sd2PinMap_h
 #error unknown chip
 #endif  // defined(__AVR_ATmega1280__)
 //------------------------------------------------------------------------------
-static const uint8_t digitalPinCount = sizeof(digitalPinMap)/sizeof(pin_map_t);
+static const uint8_t digitalPinCount = COUNT(digitalPinMap);
 
 uint8_t badPinNumber(void)
   __attribute__((error("Pin number is too large or not a constant")));

Marlin/configuration_store.cpp

     max_feedrate[i] = tmp2[i];
     max_acceleration_units_per_sq_second[i] = tmp3[i];
     #ifdef SCARA
-      if (i < sizeof(axis_scaling) / sizeof(*axis_scaling))
+      if (i < COUNT(axis_scaling))
         axis_scaling[i] = 1;
     #endif
   }

Marlin/digipot_mcp4451.cpp

   const float digipot_motor_current[] = DIGIPOT_I2C_MOTOR_CURRENTS;
   Wire.begin();
   // setup initial currents as defined in Configuration_adv.h
-  for(int i = 0; i <= sizeof(digipot_motor_current) / sizeof(float); i++) {
+  for(int i = 0; i < COUNT(digipot_motor_current); i++) {
     digipot_i2c_set_current(i, digipot_motor_current[i]);
   }
 }

Marlin/macros.h

 #define ENABLED(b) _CAT(SWITCH_ENABLED_, b)
 #define DISABLED(b) (!_CAT(SWITCH_ENABLED_, b))
 
+#define COUNT(a) (sizeof(a)/sizeof(*a))
+
 #endif //__MACROS_H

Marlin/stepper.cpp

     pinMode(E0_MS1_PIN,OUTPUT);
     pinMode(E0_MS2_PIN,OUTPUT);
     const uint8_t microstep_modes[] = MICROSTEP_MODES;
-    for (uint16_t i = 0; i < sizeof(microstep_modes) / sizeof(microstep_modes[0]); i++)
+    for (uint16_t i = 0; i < COUNT(microstep_modes); i++)
       microstep_mode(i, microstep_modes[i]);
   #endif
 }

Marlin/thermistortables.h

 #define THERMISTORTABLES_H_
 
 #include "Marlin.h"
+#include "macros.h"
 
 #define OVERSAMPLENR 16
 
 
 #ifdef THERMISTORHEATER_0
 # define HEATER_0_TEMPTABLE TT_NAME(THERMISTORHEATER_0)
-# define HEATER_0_TEMPTABLE_LEN (sizeof(HEATER_0_TEMPTABLE)/sizeof(*HEATER_0_TEMPTABLE))
+# define HEATER_0_TEMPTABLE_LEN COUNT(HEATER_0_TEMPTABLE)
 #else
 # ifdef HEATER_0_USES_THERMISTOR
 #  error No heater 0 thermistor table specified
 
 #ifdef THERMISTORHEATER_1
 # define HEATER_1_TEMPTABLE TT_NAME(THERMISTORHEATER_1)
-# define HEATER_1_TEMPTABLE_LEN (sizeof(HEATER_1_TEMPTABLE)/sizeof(*HEATER_1_TEMPTABLE))
+# define HEATER_1_TEMPTABLE_LEN COUNT(HEATER_1_TEMPTABLE)
 #else
 # ifdef HEATER_1_USES_THERMISTOR
 #  error No heater 1 thermistor table specified
 
 #ifdef THERMISTORHEATER_2
 # define HEATER_2_TEMPTABLE TT_NAME(THERMISTORHEATER_2)
-# define HEATER_2_TEMPTABLE_LEN (sizeof(HEATER_2_TEMPTABLE)/sizeof(*HEATER_2_TEMPTABLE))
+# define HEATER_2_TEMPTABLE_LEN COUNT(HEATER_2_TEMPTABLE)
 #else
 # ifdef HEATER_2_USES_THERMISTOR
 #  error No heater 2 thermistor table specified
 
 #ifdef THERMISTORHEATER_3
 # define HEATER_3_TEMPTABLE TT_NAME(THERMISTORHEATER_3)
-# define HEATER_3_TEMPTABLE_LEN (sizeof(HEATER_3_TEMPTABLE)/sizeof(*HEATER_3_TEMPTABLE))
+# define HEATER_3_TEMPTABLE_LEN COUNT(HEATER_3_TEMPTABLE)
 #else
 # ifdef HEATER_3_USES_THERMISTOR
 #  error No heater 3 thermistor table specified
 
 #ifdef THERMISTORBED
 # define BEDTEMPTABLE TT_NAME(THERMISTORBED)
-# define BEDTEMPTABLE_LEN (sizeof(BEDTEMPTABLE)/sizeof(*BEDTEMPTABLE))
+# define BEDTEMPTABLE_LEN COUNT(BEDTEMPTABLE)
 #else
 # ifdef BED_USES_THERMISTOR
 #  error No bed thermistor table specified