Convert from jbuilder to dune

[emillon]

This uses dune-the-binary, dune-the-file-format as well as some idioms ((test) stanza, :standard). I'm not sure if it's worth passing -safe-string by hand these days - if that's not the case we can just remove (flags) completely.

[hannesm]

@emillon I'm fine with using dune defaults, and not pass -safe-string manually in the mirage ecosystem

[emillon]

@hannesm thanks, I removed (flags) to get the default ones.

[Drup]

Can you remind me of which warning/errors are going to be enable/disable because of this? The warnings were carefully chosen.

[emillon]

The warnings numbers correspond to the following:

 40 Constructor or label name used out of scope.
 42 Disambiguated constructor or label name (compatibility warning).
 44 Open statement shadows an already defined identifier.
 48 Implicit elimination of optional arguments.
 15 Private method made public implicitly.

I'm not sure why -warn-error -15 is used since by default it is not a fatal warning.

[Drup]

No, I meant, what is the difference between our warnings, and the one enable/disabled by dune by default.

[emillon]

It seems that dune suppresses the additional following warnings:

4 Fragile pattern matching: matching that will remain complete even
if additional constructors are added to one of the variant types
matched.
29 Unescaped end-of-line in a string constant (non-portable code).
41 Ambiguous constructor or label name.
45 Open statement shadows an already defined label or constructor.
58 Missing cmx file
60 Unused module declaration

[Drup]

Right, the additional ones are fairly debatable, so I'm okay with using the defaults.

[emillon]

Thanks. I just rebased this on top of master.