Expose internal API marked as internal

Expose internal API and mark it as x-internal so any use of such API is maked
with warning in eclipse PDE. This is approach eclipse uses as well, so devs
still can use internal API on theyr own risk.

In our case we'd like to expose Tern/Modules project properties under different
category.
Why do you add TernModulesPropertyPage inside tern.eclipse.ide.jsdt? This page is already added inside tern.eclipse.ide.ui ?