opam 2.0.3-1 fails on init due to incorrect solver dependencies

[Anil Madhavapeddy]

opam 2.0.3 in debian-testing and Ubuntu 19.04 seems to fail on init due to being compiled with solver dependencies that are not the ones recommended by upstream opam. The symptoms are:

```
# opam init -ya
<snip>
<><> Creating initial switch (ocaml-system>=4.02.3) <><><><><><><><><><><><><><>
[ERROR] Solver failed: "/usr/bin/aspcud /tmp/opam-xxx-4699/solver-in-4699-548b09 /tmp/opam-xxx-4699/solver-out-4699-8b8a2d
        -count(removed),-sum(request,version-lag),-count(down),-sum(solution,version-lag),-count(changed)" exited with code 1 "ERROR:
        grounder returned with non-zero exit status
```

The Debian bug report is at: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=908203

I maintain a PPA at avsm/ppa that does work, but is not suitable for upstreaming (its just to get the working opam binary into CI easily).

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.