add atdgen.1.2.4
add biniou.1.0.6
add yojson.1.1.6
refine atdgen.1.2.3 constraints to need biniou.1.0.6
the older yojson.1.1.3 has a fixed upper bound on biniou version
Merge pull request #719 from mirage/master

refresh atdgen packages