[DONTMERGE] Test ranked_index #18977

This is a simple test to see if boost multi_index's ranked_index works in Travis.

Do not merge.

It seems Ubuntu 16.04 (xenial) only has boost 1.58.

See #16381 #18943

Xenial's C++ compiler doesn't support C++17 (#16684) so we're going to get rid of build-time support for that anyhow. I wouldn't mind dropping it sooner if you really need this (for 0.21, I mean; backporting any of this to 0.20 is out of the question).

(also even after the minimum bump, if people really insist on building on xenial, they can use the boost from depends which is 1.70)

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Conflicts

Reviewers, this pull request conflicts with the following ones:

• #18740 (Remove g_rpc_node global by ryanofsky)

If you consider this pull request important, please also help to review the conflicting pull requests. Ideally, start with the one that should be merged first.

xenial ships also with clang-8, so that should compile C++17 . But I agree that at this point we should be comfortable to tell people to use depends on xenial.

For reference, the OS version breakdown of the snap package is:

• 45% bionic
• 15% 19.10
• 10% focal
• 5% xenial
• 5% linux mint
• x% some other non-Ubuntu OSes

Thanks for the information everyone. This may end up being useful, but it seems there is a better solution that doesn't need this.