...messages like:

> workdir/UnpackedTarball/boost\boost/bimap/detail/map_view_iterator.hpp(138,18):  error: unqualified friend declaration referring to type outside of the nearest enclosing namespace is a Microsoft extension; add a nested name specifier [-Werror,-Wmicrosoft-unqualified-friend]
>     friend class iterator_core_access;
>                  ^
>                  ::boost::iterators::

Change-Id: I393b7c95943a55d5f755cfed41e0b7bc3306c568
Reviewed-on: https://gerrit.libreoffice.org/47673Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Stephan Bergmann <sbergman@redhat.com>