configure.ac: install GtkBuilder interface files for GTK+3 too
configure.ac: install GtkBuilder interface files for GTK+3 too

Signed-off-by: Jussi Kukkonen <589e25658b1bfd3646cd0c60eea9e9594b5e0b5b@intel.com>
Signed-off-by: Dengke Du <4d8e04faf7a99241c23d9629e3bff27fb0b9c782@windriver.com>

heftig/avahi,heftig/avahi,lathiat/avahi,lathiat/avahi,lathiat/avahi,lathiat/avahi,lathiat/avahi,heftig/avahi,lathiat/avahi,heftig/avahi,heftig/avahi,heftig/avahi