Bug: 513735 -export some packages as provisional API

Eclipse PMC discussed that yesterday and decide that we should not harm
the contributor by disallowing him to use his own code.

Change-Id: I93fad9fac7c8b7ee519aa8ef9536a9bfd53ffb0f
Reviewed-on: https://git.eclipse.org/r/c/platform/eclipse.platform.debug/+/185741
Tested-by: Platform Bot <platform-bot@eclipse.org>
Reviewed-by: Lars Vogel <Lars.Vogel@vogella.com>