Add the right constructor to Java annotations

[odersky]

Review by @olhotak please.

[DarkDimius]

@odersky error that is seen for annotaions by @olhotak is not specific to annotations.
By enabling transformation of trees inside annotations I'm still able to observe problem with
elimRepeated.

I've added a testcase that shows it.

[odersky]

My patch was not intended to fix elimRepeated. The error it addresses is much more basic than that. The patch allows annotations with arguments and allos default arguments to be elided.

[odersky]

What should we do with this? I think Ondrej will need the original commit. The question of transforming annotations is a separate one.

[DarkDimius]

I agree that the question of transforming annotations is a separate one.
With annotations I believe we need a better definition what they are and what they mean. If annotations are simple constructor calls with constant arguments than the only face that seems to be concerned with transforming annotations is elimRepeated and 2 commits in this branch will allow it to work.

If trees can be more complicated than I seems reasonable to have the tree inside the annotation be transformed on the definition side only with a definition context and this should be propagated(eg by propagating not of the annotation itself but the indirection reference to original annotated symbol).