debian: 64-bit time_t transition.

debian: 64-bit time_t transition.

As part of the 64-bit time_t transition required
to support 32-bit architectures in 2038 and beyond
(https://wiki.debian.org/ReleaseGoals/64bit-time), we have identified
liblopsub as a source package shipping runtime libraries whose ABI
either is affected by the change in size of time_t, or could not be
analyzed via abi-compliance-checker (and therefore to be on the safe
side we assume is affected).

To ensure that inconsistent combinations of libraries with their
reverse-dependencies are never installed together, it is necessary
to have a library transition, which is most easily done by renaming
the runtime library package.

Since turning on 64-bit time_t is being handled
centrally through a change to the default dpkg-buildflags
(https://bugs.debian.org/1037136), it is important that libraries
affected by this ABI change all be uploaded close together in time.
Therefore I have prepared a 0-day NMU for liblopsub which will
initially be uploaded to experimental if possible, then to unstable
after packages have cleared binary NEW.

Signed-off-by: Andre Noll <maan@tuebingen.mpg.de>