speakup-r functionality

[Okash Khawaja]

On Sun, May 28, 2017 at 06:38:39PM -0400, John Covici wrote:
> I just have one question -- how did it work with the old serial i/o
> system?
In main.c, handle_cursor_read_all calls spk_get_index_count which calls
spk_ttyio_in_nowait or spk_serial_in_nowait depending on whether TTY or
old serial i/o is in use. So the difference is in spk_serial_in_nowait
as the layers above that are identical. spk_serial_in_nowait returns 0
when there is no data on rx. spk_ttyio_in_nowait immitates that but due
to the signedness bug, it was returning 0xff instead of 0 when there
is no data.

With the fix, now both serial i/o and TTY stacks  should have same
behaviour.