Bug 416339 - [JFace] The used input types for the generic JFace API are
too restrictive!
[JFace] added generics to the ArrayContetProvider

Changed synchronized block for ArrayContentProvider.getInstance()
to provide a threadsafe access

Change-Id: I7fe2cc110cac548e59bdbb987361efa2867d3ce8
Signed-off-by: Hendrik Still <hendrik.still@gammas.de>