Passing a socket name without a trailing nul byte to uv_pipe_bind2() or
(on Windows) uv_pipe_connect2() resulted in reading beyond the end of
the name buffer when copying or converting it.
Fix that by copying the socket name to temporary storage first and add
the trailing nul byte explicitly.
Add a check for embedded nul bytes in the socket name.
Fix a small memory leak in the Windows error path of uv_pipe_bind2().
