The "new" LUFA Bootloader referenced in 1.6.9

[Jesse Vincent]

Hi folks,

I'm trying to track down the ATmega bootloader changes referenced in 1.6.9, since we're using a Caterina-derived bootloader on the keyboard we'll be shipping later this year. 

Martino added the code in commit 4c901d3f9f347177b3f263c451885ddc3b1b6ab0

The commit message says it "should work with every LUFA-derived bootloader released after 2014", but the last change I see to the Caterina source is from the 1.0.3 merge in 2012. (https://github.com/arduino/Arduino/commits/master/hardware/arduino/avr/bootloaders/caterina/Caterina.c)

Poking through pull requests, it looks like there's a chance that this is a speculative change for some other unmerged change to the bootloader and doesn't actually provide any additional functionality or fix any issues for devices with "official" Arduino/Genuino bootloaders. Is that right?

As a side note: referring to an external dependency as 'new' or 'updated' in code has a habit of bitrotting as newer, better things come along. I'm happy to submit a PR with better naming, once I understand what the new/updated bit refers to.

Best,

Jesse