Real-time filament diameter measurement and control

This feature allows the printer to read the filament diameter
automatically and adjust the printer in real time.  Added code to read
an analog voltage that represents a filament diameter measurement.  This
measurement is delayed in a ring buffer to compensate for sensors that
are a distance away from the extruder.  The measurement is used to
adjust the volumetric_multiplier for the extruder.  Some additional g
codes (M404, M405, M406, M407) are used to set parameters and turn
on/off the control. g code M221 is updated.  Pins for RAMPS1.4, RAMBO,
and Printrboard are identified for analog input.  The configuration file
is updated with relevant user parameters.

Marlin/pins.h

@@ -558,6 +558,15 @@
     #define E1_DIR_PIN         34
     #define E1_ENABLE_PIN      30
 
+#if MOTHERBOARD == 34  //FMM added for Filament Extruder
+#ifdef FILAMENT_SENSOR
+	  //define analog pin for the filament width sensor input
+	  //Use the RAMPS 1.4 Analog input 5 on the AUX2 connector
+      #define FILWIDTH_PIN        5
+#endif
+#endif
+
+
     #if MOTHERBOARD == 68
       #define E2_STEP_PIN        23
       #define E2_DIR_PIN         25
@@ -1692,6 +1701,9 @@
   #define Z_STOP_PIN         36
   #define TEMP_0_PIN          1  // Extruder / Analog pin numbering
   #define TEMP_BED_PIN        0  // Bed / Analog pin numbering
+  #ifdef FILAMENT_SENSOR
+   #define FILWIDTH_PIN        2
+  #endif //FILAMENT_SENSOR
 #endif
 
 #define TEMP_1_PIN         -1
@@ -2326,6 +2338,10 @@ DaveX plan for Teensylu/printrboard-type pinouts (ref teensylu & sprinter) for a
   #endif
 #endif //ULTRA_LCD
 
+#ifdef FILAMENT_SENSOR
+  //Filip added pin for Filament sensor analog input 
+  #define FILWIDTH_PIN        3
+#endif //FILAMENT_SENSOR
 
 #endif