Define the __notused token to declare unused parameters

Note that this has not been named __unused because the name triggers
issues in <sys/stat.h>.

Signed-off-by: Paul Cercueil <paul.cercueil@analog.com>
IIOD: Register with Avahi if available

Signed-off-by: Paul Cercueil <paul.cercueil@analog.com>
Network backend: Use ZeroConf to find the IIO daemon when host is NULL

When a NULL value is passed to the "host" parameter of
iio_create_network_context(), the network backend will now search for a
IIOD daemon using ZeroConf, provided it was compiled with support for
Avahi.

Signed-off-by: Paul Cercueil <paul.cercueil@analog.com>