Prevent extremely long command line arguments from overflowing local
buffers in raw_printf or config_error_add. The increased buffer
sizes they recently got to deal with long configuration file values
aren't sufficient to handle command line induced overflows.
choose_windows(core): copy and truncate the window_type argument in
case it gets passed to config_error_add().
process_options(unix): report bad values with "%.60s" so that vsprintf
will implicitly truncate when formatted by raw_printf().
f3def5c0b9