create a plugin that finds methods we can mark as final because they are
not override in subclasses.
Which is useful both as documentation (telling you that you don't need
to worry about subclasses changing the implementation under you),
and for performance, letting the compiler elide virtual calls in many
cases.
Apply the results to a subset of stuff in /include
Change-Id: I7b5cc893ec2f343bc356bfc338e4cf531ffba1e0
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/165054
Tested-by: Jenkins
Reviewed-by: Noel Grandin <noel.grandin@collabora.co.uk>
