devel/mgdiff installed from pkgin can't find app-defaults

[Monica Vaida <vaidamonica587%gmail.com@localhost>]

Hello all,
```mgdiff``` installed by ```pkgin``` can not find its app-defaults.
They exist under ```/usr/pkg/lib/X11/app-defaults``` but it seems that
```mgdiff``` was not compiled to look there.
Thank you.