Corretions and refinements to the String examples

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

@@ -15,11 +15,13 @@
 void setup() {
   // Open serial communications and wait for port to open:
   Serial.begin(9600);
-  // this check is only needed on the Leonardo:
-  while (!Serial) ;
-  ;
+  while (!Serial) {
+    ; // wait for serial port to connect. Needed for Leonardo only
+  }
 
+  // send an intro:
   Serial.println("\n\nString  substring():");
+  Serial.println();
 }
 
 void loop() {