Updated all serial in setup examples with a note about the serial check

build/shared/examples/08.Strings/StringComparisonOperators/StringComparisonOperators.ino

@@ -17,7 +17,9 @@ String stringOne, stringTwo;
 void setup() {
  // Open serial communications and wait for port to open:
   Serial.begin(9600);
-  while(!Serial) ;
+  // this check is only needed on the Leonardo:
+  while (!Serial) ;
+ ;
 
   stringOne = String("this");
   stringTwo = String("that");