OSGi has support for annotations that are only retained at the class
file (but not on the runtime) to help tools generating meta-data or
perform several checks.

This adding them to the compile-classpath without requiring the bundle
developer to import them (what would create an undesired runtime binding
to those packages) if they are found in the target platform.

This is part of https://github.com/eclipse-pde/eclipse.pde/issues/69