merge the droplong and convertuintptr into one new plugin.
Limit the analysis to looking at var decl's, since that seems to be
safest proposition, even if that too needs some careful analysis.

Change-Id: Id005baaf05cfb157ce44a06a1c81f08559a07d1f
Reviewed-on: https://gerrit.libreoffice.org/46851Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Noel Grandin <noel.grandin@collabora.co.uk>