Documentation/features: Add script that refreshes the arch support status files in place

Provides the script:

	Documentation/features/scripts/features-refresh.sh

which operates on the arch-support.txt files and refreshes them in place.

This way [1],

   "[...] we soft- decouple the refreshing of the entries from the
    introduction of the features, while still making it all easy to
    keep sync and to extend."

[1] http://lkml.kernel.org/r/20180328122211.GA25420@andrea



Suggested-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Andrea Parri <andrea.parri@amarulasolutions.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>