Clean up so that only the following error related printing functions are
used: tio_error_printf(), tio_error_printf_silent(),
tio_warning_printf().
A session mode switch is introduced for error printing so that it will
print error messages with better formatting depending on in or out of
session.
Logfiles are important to see what happend, in particular if something
unexpected happened; so we want to make sure that the logfile is flushed
to disk.
Before this change, the logfile was typically written at the end in
a large chunk as the default (large) buffering applied. Now, characters are
written out ASAP, so it is possible to get a live-view with a
tail -f <logfile>
Renamed to "tio" because it is shorter and this new name also more
precisely reflects what the program is - a simple TTY terminal I/O
application.
"tio" can be considered short for terminal I/O or TTY I/O or a
combination of the two, whichever you prefer.
Also, wanted to avoid naming conflicts with other projects.
