Removal of those have to be decided manually:

1) If it would be removed to be replaced with an include, that's bad.

2) If the fwd decls is truly unused, that's good.

Focus on the mechanical part: removal of includes which are unused, and
where removal doesn't introduce a transitive dependency.

Verified that e.g. writerfilter/source/dmapper/DomainMapper.cxx reports
no removals now, but including e.g. filter/msfilter/rtfutil.hxx in
either writerfilter/source/dmapper/DomainMapper.cxx or
writerfilter/source/dmapper/DomainMapper.hxx triggers a removal hint.

Change-Id: I4c359318113ccba421a125984e23c9778567ea4e
Reviewed-on: https://gerrit.libreoffice.org/73240Reviewed-by: Miklos Vajna <vmiklos@collabora.com>
Tested-by: Jenkins