Add warnings when a type or method is not found in introspection.
Add warnings when a type or method is not found in introspection.

This makes debugging easier than when non-existing methods just ended
up not doing anything.

Distrotech/libpeas,GNOME/libpeas,Distrotech/libpeas,GNOME/libpeas,gregier/libpeas,gregier/libpeas,chergert/libpeas,gregier/libpeas,gregier/libpeas,chergert/libpeas,Distrotech/libpeas,chergert/libpeas