This #ifdeffed out TEST_CARD is useful for javascript code that shows how a
theme will look, when applied to Audacity. With the code enabled, each
pixel of audacity is painted with a colour that encodes the location in
the theme image map that was used.
Net result - in javascript you can change any colour in the theme cache
and instantly see how Audacity will look.
100% transparent black was appearing as black. Now it appears as the background colour.
AButton backgrounds now support alpha channel, which they did not before.
