Fixup windows PCH plus pulling out more code now unused due to NPAPI
removal. Follow-up to 4c18af27.

Change-Id: I8ad42a28139ceeab0cae1f608d55beb28c159db3
Reviewed-on: https://gerrit.libreoffice.org/20783Reviewed-by: Thorsten Behrens <Thorsten.Behrens@CIB.de>
Tested-by: Thorsten Behrens <Thorsten.Behrens@CIB.de>