This patch allows scripts to have more control over the software WDT. If
an instance of machine.WDT is created then the underlying OS is prevented
from feeding the software WDT, and it is up to the user script to feed it
instead via WDT.feed(). The timeout for this WDT is currently fixed and
will be between 1.6 and 3.2 seconds.
This is to keep the top-level directory clean, to make it clear what is
core and what is a port, and to allow the repository to grow with new ports
in a sustainable way.