Do no modify terminal parameters using termios.h

Remove usage of tcgetattr and tcsetattr to modify terminal
parameters, and rely on ctrl-c to stop instead of pressing 'q'.
On systems with conio.h, keep the old behavior.

Changing the terminal settings causes problems if multiple instances
are running asynchronously on the same terminal, such as during a
parallel FATE run, or if the process crashes before restoring the
terminal.  In both cases, the terminal state is messed up requiring
a manual reset.

Signed-off-by: Mans Rullgard <mans@mansr.com>