py/stream: Introduce MP_STREAM_GET_FILENO ioctl request.
Can be used by POSIX-like systems that associate file numbers with a file.
#define MP_STREAM_SET_OPTS (7) // Set stream options
#define MP_STREAM_GET_DATA_OPTS (8) // Get data/message options
#define MP_STREAM_SET_DATA_OPTS (9) // Set data/message options
+#define MP_STREAM_GET_FILENO (10) // Get fileno of underlying file
// These poll ioctl values are compatible with Linux
#define MP_STREAM_POLL_RD (0x0001)
