For the vendor code to make it through string conversions unharmed, we should make it part of the printable ASCII subset. Fixes compatibility with xusb when reading WCID descriptor.

This is some Microsoft-specific gunk which allows us to work with usermode apps without any onerous driver installation. Much better user experience!

Otherwise, some call sites will certainly forget this...

Sometimes we might want host-side software to control it, or even to just turn it off.

This is necessary for reprogramming a Fadecandy board without access to the physical button.

The firmware is feature-complete now, and this will save folks the trouble of downloading a huge toolchain. Plus I like to keep tabs on the quality of the assembly output :)