Bring back DEBUG key

[regicidalplutophage]

No description provided.

[xs5871]

You know what... maybe you were right the first time. The autodebug should cover 98% of usecases. The single use I have for it is to halt debug output if I see something interesting and don't want the scrollback buffer to eventually write over it. That's a personal workflow issue and can easily be solved differently.
I keep saying we shouldn't put convenience utility in the core firmware that only caters to a negligible amount of users, and it may be my time to either live without it or make it part of my personal config.