Fix from blargg-adb-teensy-2.zip

- http://geekhack.org/index.php?topic=14290.msg1118206#msg1118206
* Changed polling to 12ms (83Hz). Works better with M0116. Can still be
* adjusted back to 8ms (125Hz) in main.c
* Fixed dropped key when it's pressed and released in same ADB event.
* Reorganized code to be in sync with v-usb version.
* Disable interrupts for all ADB transactions.
* Send each ADB event byte as a separate USB report. This ensures things
* are in order and cleanly handles cases when the same key is pressed
* then released in a single ADB event.