Fix Windows client's stdin read thread's error handling

Fix Windows client's stdin read thread's error handling

stdin_read_thread() zeroed bounce_status on failure, effectifely
treating it like EOF.  Fix by setting to -1.

It treated main thread termination like failure, and set bounce_error
to a bogus value.  Can't happen, because the program terminates when
the main thread terminates, and the only user of bounce_error is the
main thread anyway.  Regardless, handle the case by terminating,
because that's more obviously correct.

Broken in commit f082ef9f, v4.3.11.