libgupnp-dlna: add 'relaxed' and 'extended' mode properties
libgupnp-dlna: add 'relaxed' and 'extended' mode properties

This patch adds properties on the GUPnPDLNADiscoverer class for
'relaxed' mode and 'extended' mode support. These will be supported
in the next release.

GNOME/gupnp-dlna,luisbg/gupnp-dlna,GNOME/gupnp-dlna,GNOME/gupnp-dlna,luisbg/gupnp-dlna