Patch Set 4: I would prefer that you didn't submit this

According to [1] we should export all packages and mark those x-internal we don't consider to be API. This change currently solves this issue only partially.

I am not sure if the following packages (which are currently not exported) are meant to be non-internal (they don't have "internal" in their package name):
* org.eclipse.egit.ui.credentials
* org.eclipse.egit.ui.variables

@Robin, Jens: was this by intention ?

[1] http://wiki.eclipse.org/Export-Package