Both dialogs got a couple extra radio buttons for selection of
single character operands. The data operand editor got a combo box
that lets you specify how it scans for viable strings.
Various string scanning methods were made more generic. This got a
little strange with auto-detection of low/high ASCII, but that was
mostly a matter of keeping the previous code around as a special
case.
Made C64 Screen Code DCI strings a thing that works.
