Swap the order of the default and custom callback registration, since
the order of lookup is now reversed since
<https://github.com/lsh123/xmlsec/commit/968646fb9b8428174a112fce2f08b1ec89d0ed97>.

Thanks Tomas Chvatal for reporting this.

(cherry picked from commit 576f8998)

xmlsecurity: check for the libxmlsec version runtime, not build-time

For the general benefit of --with-system-xmlsec usage scenarios (where
LO may be built against an old version of xmlsec and run against a new
one).

(cherry picked from commit bc4e43dd)

Change-Id: I60a347454701a679db4ccd8924a723a236d5edff
Reviewed-on: https://gerrit.libreoffice.org/55462Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Miklos Vajna <vmiklos@collabora.co.uk>
(cherry picked from commit 3d532502)
Reviewed-on: https://gerrit.libreoffice.org/55944
Tested-by: Jenkins
(cherry picked from commit 355a59a7)