Added support for PCBoard @ macros:

- DELAY:nn (delay nn 10ths of a second)
- POS:nn (move cursor to position nn, not sure if nn is 0 or 1-based)
- CLREOL (same as CLR2EOL)
- YESCHAR (the character/key for "Yes", from text.dat YNQP string)
- NOCHAR (the character/key for "No', from text.dat YNQP string)

and for good measure:
- QUITCHAR (the character/key for "Quit") - not supported by PCBoard