This is a modified conio. It doesn't draw a cursor at all.

More particularly, the standard cc65 conio always draws a cursor, whether
the cursor is enabled or not. When it's disabled, the cursor is drawn
as a space character.

Also, the cputc() here no longer requires \r\n to move the cursor
to the start of the next line. \n alone does it, and \r isn't
treated specially (it's just a ctrl-R, prints a graphics character).

The cputcxy() routine has been deleted, since taipan doesn't use it.

Benefits of doing this:

- Faster and smoother screen updates
- Slightly smaller code (100-odd bytes)
- No more "cursor ghosts" at timed prompts
- No need for a hide_cursor() function
- print_msg() from textdecomp.s is simplified, it no longer has
  to print a carriage return every time it sees a newline in a
  compressed message.
- In taipan.c, cputs("foo\r\n") no longer requires the \r, saves
  one byte per string.

Disadvantage: Have to draw the cursor myself when needed. It turns out
that only agetc() needs to do this, so not a big deal. Also had to
add an agetc_no_cursor() for timed_getch() to use.