DSAnnotationCompilationParticipant

Used upcoming JDT cleanup to replace this usage in PDE, StringBuilder is
not synchronized and hence should be preferred.

Change-Id: I8515af84d76a6878da77e0bb341d6ace38089618
Signed-off-by: Lars Vogel <Lars.Vogel@vogella.com>
Reviewed-on: https://git.eclipse.org/r/c/pde/eclipse.pde.ui/+/181498
Tested-by: PDE Bot <pde-bot@eclipse.org>