dpkg --force-depends -r libntl0
dpkg --force-depends -r libntl-dev
apt-get install libntl-dev
(and similarly for flint).
I think those may be the only ones that will have that particular problem
in upgrading from my repo to the packages in Debian's archive.
I suspect the SAGE package itself won't work after you do the upgrade,
though, since it'll have been compiled against the older versions of flint
and ntl.
I'm afraid that at the moment, my repository lacks a working sage
installation.
On the other hand, I'm getting close to having all the SAGE dependencies
in Debian itself that I need.
As usual, the big blocker is still getting a 0.4 or later version of
polybori working in SAGE.
-Tim Abbott