yad: new package

[Thomas: remove dependency on libglib2, as it is not tested directly
by yad's configure script, and is anyway guaranteed to be available
since yad depends on gtk2 or gtk3, which both require libglib2.]

Signed-off-by: James Knight <james.knight@rockwellcollins.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>