Also the last few remaining occurrences of the header

Since it is now possible to use C++14, it's time to replace
the temporary solution with the standard one

Change-Id: I18f435270057f2d09e21d6ea262532cbcc974598
Reviewed-on: https://gerrit.libreoffice.org/67843
Tested-by: Jenkins
Reviewed-by: Miklos Vajna <vmiklos@collabora.com>