Depends on gringo but gringo is now maintained as part of the clingo
suite. This commit removes gringo (standalone) and replace it with
the latest version of clingo. This update follows closely the old
derivation for gringo (see 99e06fe).
The opam package manager relies on external solvers to determine package
management decisions it makes related to upgrades, new installations,
etc.
While, strictly speaking, an external solver is optional, aspcud is
highly recommended in documentation. Furthermore, even having a
relatively small number of packages installed quickly causes the limits
of the interal solver to be reached (before it times out).
Aspcud itself depends on two programs from the same suite: gringo, and
clasp.
On Darwin, Boost 1.55 (and thus Gringo) do not build, so we only support
Aspcud on non-Darwin platforms.
