new component: hw-visual-probe-pin

[Frank Ch. Eigler]

Hi -

A few hours' hacking resulted in another demonstration widget that aims
to show off the kinds of monitoring components that may be easily inserted
into a sid simulation.  It's written in tcl/tk, and has a single input pin
on which it receives stimulus.  One could configure it something like
this; though any old output pin that spits out a range of values might
be interesting.

	new hw-visual-probe-pin boingo
	connect-pin boingo stimulus <- cpu step-cycles

The component displays a window filled with roving icons.  Each icon
represents a stimulus value (sid::pin::driven() argument) that has been
received.  The icons move around the screen in relationship to how
frequently/intensely each particular value is received.  It's sort of
a qualitative monitor, like lavaps and Mark Weiser's "Dangling String".
The top few icons (the ones moving fastest since they have been occurring
most frequently) are decorated with 100% genuine fuzzy dice.

By the way, this may make sid the first simulator in the world with
built-in fuzzy dice support.  I attach a screenshot as proof.

- FChE