Update to 1.2

Upstream changes:
NEWS for version 1.2  (released on February 11, 2016)
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New and Changed Features
========================

o  Improved the efficiency of the conversion procedure for polyhedra
  by adding a quick adjacency check.

o  In the Java language interface, throw an exception when trying
  to build a disequality Constraint.

Bugfixes
========

o  Fixed a bug in the implementation of methods
    Pointset_Powerset<PSET>::relation_with(const Constraint&) const;
  and
    Pointset_Powerset<PSET>::relation_with(const Congruence&) const;
  whereby the computed result for relations strictly_intersects()
  and saturates() could have been wrong.

o  Fixed a bug in the implementation of dense rows.

o  Portability improved.

(wen)