For one, replacing the dated .def files with equivalent functionality should be
a good move all by itself.  And for another, it paves the way for using
loplugin:external with clang-cl on Windows, which uses the heuristic of not
warning about functions that are explicitly marked as __declspec(dllexport).

Change-Id: I6efd50a8c5ce2a166ca0dd4e5f472118f3f9a071
Reviewed-on: https://gerrit.libreoffice.org/60691
Tested-by: Jenkins
Reviewed-by: Mike Kaganski <mike.kaganski@collabora.com>