fplll: need a big upgrade

[Julien Puydt <julien.puydt@laposte.net>]

Hi,

the version of fplll in debian is ancient, and should be upgraded. Sage
5.0 has version 3.0.12, but sage 5.1 targets version 4.0.0.

Those new versions aren't GPL anymore, but LGPL.

I'm willing to take care of it, if nobody else steps forth, as Tim
Abbott, the official maintainer, is busy.

Snark on #debian-science