Verify All `While (!Serial)` loops

[microbuilder]

All examples should be checked so that the initial Serial check waiting for Serial Monitor to be opened includes a 'delay' to avoid issues with RTOS task switching:

while (!Serial)
{
  /* Delay required to avoid RTOS task switching problems */
  delay(10);
}

Or alternatively:

while (!Serial) { yield(); }

[hathach]

all examples already has delay(1). Only a few like Blink that user modifies since it does not use Serial. Though, I will add the comment about the RTOS task to make it clearer.