Searched source for using declarations.
Checked if those symbols reappear in the source file,
even in comments or dead code but not in #include statements.
If they don't reappear, remove the declaration.
Remove includes whose symbol got removed.

Change-Id: Ibb77163f63c1120070e9518e3dc0a78c6c59fab0
Reviewed-on: https://gerrit.libreoffice.org/24148Reviewed-by: Jochen Nitschke <j.nitschke+logerrit@ok.de>
Reviewed-by: Noel Grandin <noelgrandin@gmail.com>
Tested-by: Noel Grandin <noelgrandin@gmail.com>