fuzzer tweaks

fuzzer tweaks

Prevent the fuzzer from randomly toggling the 'silent' option.  If
you use the default value of True then this eliminates most--but not
all--of the beeping that happens when it is running.  I'm not sure
where the remaining beeps are coming from.

Modify the random keystroke selection to implement some bias towards
direction keys that I thought had already been there, plus a higher
chance to entering digits to initiate number responses.