GNotification: Some small documentation fixes

Use #GVariant instead of GVariant.

g_notification_add_button_with_target,
g_notification_set_default_action_and_target:
Replace 'format_string' with 'target_format'.

g_notification_set_default_action_and_target_value:
Remove paragraph that apparently had been accidentally copied from
g_notification_set_default_action_and_target.

https://bugzilla.gnome.org/show_bug.cgi?id=727123
Updated Hungarian translation
Updated Basque language
Updated Czech translation
networkmonitornetlink: IN6_IS_ADDR_MC_LINKLOCAL is only guaranteed to work on struct in6_addr*

https://bugzilla.gnome.org/show_bug.cgi?id=727119
GApplication: Don't decrease use_count below 0

Place an assert for use_count to be at least 1
in g_application_release() so we don't decrease
it below 0.

https://bugzilla.gnome.org/show_bug.cgi?id=727551