Opam: Update to 1.1.0

Also keeps 1.0 for backwards compatibility.

Signed-off-by: Moritz Ulrich <moritz@tarn-vedra.de>
Opam 1.1: Constrain supported ocaml versions.

Signed-off-by: Moritz Ulrich <moritz@tarn-vedra.de>
calibre: upgrade from 1.15.0 to 1.17.0