Apparently bash doesn't turn off non-blocking mode on stdin/stdout when
reading from it, so be nice to bash. Ideally bash would do this on its
own for robustness reasons, though.
https://bugs.freedesktop.org/show_bug.cgi?id=70622
It was calling cfmakeraw(3) on the properties for STDIN_FILENO; cfmakeraw
sets both input and output properties. If (and only if) stdin and stdout
are the same device is this correct. Otherwise, we must change only the
input properties of stdin, and only the output properties of stdout.