Hasty change to transform callback specification breaks annotation extension.

[amcgregor]

A change made shortly before release to more cleanly support the annotation extension manipulation of the value returned by the handler was applied to the annotation extension itself, and example extension (which is the only other in-core definition of the transform callback), but failed to update Application to pass the handler as expected.

[amcgregor]

Fixed in 4e4066a, test in 35a5e87.