Port/gasoline

This is to add bsdowl v2.2 and gasoline to opam.

References:
- ocaml/opam#1812
- michipili/bsdowl#43
- michipili/gasoline#4
Is this necessary? If you'd like to remove the package's share directory contents, that path is available via the variable `bsdowl:share`. See `opam config list` for details.