* Remove chording as it is not documented, not used, and needs work.
* Make Leader Key an optional feature.
* Switch from `PREVENT_STUCK_MODIFIERS` to `STRICT_LAYER_RELEASE`
* Remove `#define PREVENT_STUCK_MODIFIERS` from keymaps.
* Copy Chibios serial_usb_driver into the chibios/protocol
It's renamed to usb_driver to avoid name conflicts
* Make the usb driver compile
* Disable ChibiOS serial usb driver for all keyboards
* Change usb_main to use QMKUSBDriver
* Initialize the usb driver buffers
* Add support for fixed size queues
* Fix USB driver initialization
* Don't transfer an empty packet for fixed size streams
* Initial K-Type support
* Copy PJRC_TEENSY_3_1 to work around watchdog issues
* K-Type: Remove bootloader offset in rules.mk
* Ensure matrix and scan quantum functions are called when needed
This is porting a fix from f5422a70b6