Bug#1106888: transition: libxml2, libxslt, xmlsec1 - one transition to bind them all

[Graham Inggs <ginggs@debian.org>]

Just an update: libxml2-16, libxslt and libxmlsec1-1 have all
migrated.  There are a couple of binNMUs still building, but now it's
just a matter of fixing or removing the remaining packages.

For the record, I ended up working from Matthias' .ben file (including
the .build-depends regex) as it appeared to deal with dependency
levels better.

I did not schedule binNMUs for any of the 'unknown' packages, as these
had neither a dependency on the old libxml2 library nor the new
libxml2-16 library.