Previously, we required the user to specify the expected read/write
flags for a pipe or tty. But we've already been asking the OS to tell us
what they actually are (fcntl F_GETFL), so we can hopefully just use
that information directly.
Fixes: https://github.com/libuv/libuv/issues/1936
PR-URL: https://github.com/libuv/libuv/pull/1964
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Santiago Gimeno <santiago.gimeno@gmail.com>
