`uv_try_write2(stream, bufs, nbufs, send_handle)` acts like
`uv_try_write()` and extended write function for sending handles over a
pipe like `uv_write2`. It always returns `UV_EAGAIN` instead of
`UV_ENOSYS` on Windows so we can easily write cross-platform code
without special treatment.
PR-URL: https://github.com/libuv/libuv/pull/3183
Reviewed-By: Jameson Nash <vtjnash@gmail.com>
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