Follow-up the PR #4955, etc

・More ANALOG NUMBERING to Analog Input
・Add comment header to all the section of all the pins files

・Sort sections as follows:
1. Some special definitions (USBCON, LARGE_FLASH, etc)
2. Servos
3. Limit Switches
4. Z Probe
5. Steppers
6. Temperature Sensors
7. Heaters / Fans
8. Misc. Functions
9. LCD / Controller

・Move MAX6675_SS into "Temperature Sensors" section
・Adjust spacing

Marlin/pins_MEGATRONICS_3.h

@@ -63,6 +63,8 @@
   #define Z_MIN_PROBE_PIN  19
 #endif
 
+#define SLED_PIN           -1
+
 //
 // Steppers
 //
@@ -90,14 +92,6 @@
 #define E2_DIR_PIN         60
 #define E2_ENABLE_PIN      23
 
-//
-// Misc. Functions
-//
-#define SDSS               53
-#define LED_PIN            13
-#define PS_ON_PIN          12
-#define SLED_PIN           -1
-
 //
 // Temperature Sensors
 //
@@ -133,6 +127,13 @@
 #define FAN_PIN             6
 #define FAN1_PIN            7
 
+//
+// Misc. Functions
+//
+#define SDSS               53
+#define LED_PIN            13
+#define PS_ON_PIN          12
+
 //
 // LCD / Controller
 //