In particular, add macros for KEY_TAB, KEY_RETURN and KEY_ESC, and for
CURS_ON and CURS_OFF (instead of using CURS_INVISIBLE and CURS_VISIBLE
directly: this allows redefining CURS_ON to be CURS_NORMAL). Add more
colour pairs.
Also define WIN_COLS and WIN_LINES: the current version of Star Traders
will only use this number of lines and columns in a terminal window. All
calls to newwin() need to have COL_OFFSET and LINE_OFFSET added to the X
and Y starting positions to make this work.