Generated specialized Functional Interfaces for Function{0,1,2}

As exerciced in the test, a specialized (Int => Int) function can
be implemented by extending the functional interface
`JFunction1$mcII$sp`.
Add a hook to the build to disable doc publishing and genjavadoc

Handy when varying other build parameters, such as `scalaVersion`,
results in unavailabilty of genjavadoc or in a Scaladoc bug.