ty: pick up new keyboard scanner workaround from m65

[dansanderson]

The new keyboard scanner in the latest development core and ROM is too fast for the virtual keyboard registers as used by m65 and m65dbg. In m65, I was able to work around this like so, separating the Shift and key settings into separate s commands:

MEGA65/mega65-tools@4ca0bd2

m65dbg will need a similar change. There are currently no plans to fix the virtual keyboard registers to support the other method. (They ought to be, I just don't know anyone who is working on it.)