screenmode: fix MIME signature

Change-Id: Id7f1ffea799b4843076abe4e791d949dcb2f0339
Reviewed-on: https://review.haiku-os.org/c/haiku/+/2518
Reviewed-by: waddlesplash <waddlesplash@gmail.com>

Signature have to match in rdef and sources.

Change-Id: I4172585fab51e9d9640ae7a40b5b9c3a247fb841
Reviewed-on: https://review.haiku-os.org/711
Reviewed-by: waddlesplash <waddlesplash@gmail.com>

Allow to change brightness from the command line

screenmode can now set the brightness (only for intel_extreme, still).
Both absolute and relative values are accepted, allowing to bind
keyboard shortcuts to "increase brightness" and "decrease brightness".

Change-Id: I5221532ebdfba5df1b4d4e1f3331406359f2807c
Reviewed-on: https://review.haiku-os.org/655
Reviewed-by: Kacper Kasper <kacperkasper@gmail.com>