- fixed the videx-like keymappings for the upper/lower keyboard
- moved @ to SHIFT-0 from CTRL-0, and put ID on CTRL-0
- bind the applesoft key test program to CTRL-3
- cram the keyboard test program into one line, to avoid adding a delay
for BASIC parsing after the CR.
- in main(), output only printable codes less than INVALID_CODE,
- instead of checking for code != INVALID_CODE.
- asdf_keymaps_select_keymap() function to select a keymap
- asdf_keymaps_select_n_{set|clear} functions to set a bit in keymap number,
to support dip switches.
