Suspend call currently exits ca mode. So after the first suspend/resume
the program does not use the alternate screen anymore. Therefore Resume
needs to enter ca mode again.
fixes#194 Starting multiple screen sessions (lost key event)
You can test this by using the mouse demo, which now supports pressing
CTRL-Z. This does not actually suspend the demo, but starts a subshell
which takes over. After the subshell is exited, the demo takes control
of the screen back. This can be done multiple times, and it is possible
to start multiple "nested" iterations of the demo this way.
This does sort the main problem of screen.Fini(), but really we
want to use a separate Pause() and Resume() function, because
screen.Fini() is not meant for reuse in this way.
Note that one side effect of this change is that applications which
redirect stdin and stdout and expect us to just use /dev/tty instead
are going to break -- we are now using stdin and stdout like nearly
every other screen oriented application.
