Fixed Smoothing example

"index" variable name create conflicts with Arduino Due where "index" is
a reserved word for Posix C.

Author: cmaglie

build/shared/examples/03.Analog/Smoothing/Smoothing.ino

@@ -28,7 +28,7 @@
 const int numReadings = 10;
 
 int readings[numReadings];      // the readings from the analog input
-int index = 0;                  // the index of the current reading
+int readIndex = 0;              // the index of the current reading
 int total = 0;                  // the running total
 int average = 0;                // the average
 
@@ -45,18 +45,18 @@ void setup()
 
 void loop() {
   // subtract the last reading:
-  total= total - readings[index];         
+  total= total - readings[readIndex];         
   // read from the sensor:  
-  readings[index] = analogRead(inputPin); 
+  readings[readIndex] = analogRead(inputPin); 
   // add the reading to the total:
-  total= total + readings[index];       
+  total= total + readings[readIndex];       
   // advance to the next position in the array:  
-  index = index + 1;                    
+  readIndex = readIndex + 1;                    
 
   // if we're at the end of the array...
-  if (index >= numReadings)              
+  if (readIndex >= numReadings)              
     // ...wrap around to the beginning: 
-    index = 0;                           
+    readIndex = 0;                           
 
   // calculate the average:
   average = total / numReadings;