Replace the Bro language with Zeek

[jsiwek]

Bro was officially renamed to Zeek in this announcement. The primary file extension will be
.zeek, but .bro is also still supported. In either case, the language should now be identified as "Zeek" instead of "Bro". The master branch of the main Zeek repository has already converted to using the .zeek extension.

The external grammar definition, "bro-sublime", is now "zeek-sublime".
The later has updates that reflect the name change and some further
improvements. Lightshow comparisons:

Real-world sample OLD source.bro
Real-world sample NEW source.zeek
Real-world sample source file
Real-world sample license

Contrived sample OLD source.bro
Contrived sample NEW source.zeek
Contrived sample source file
Contrived sample license

Both samples are included in this commit.

Checklist:

• I am REPLACING an existing language name, adding a new file extension for it, and updating its grammar submodule all at once

  • The new extension is used in hundreds of repositories on GitHub.com

    • Not yet, but as explained above, the language name itself is changing, so expect similar adoption eventually. The original .bro extension is used within the order of a hundred repos just counting what's listed on our public, user-submitted package repository.
      • GH .bro search results
      • GH .zeek search results

  • I have included a real-world usage sample for all extensions added in this PR:

    • Sample sources + licenses listed above.

  • I have included a change to the heuristics to distinguish my language from others using the same extension.

    • N/A

[pchaigno]

Thanks for the neat pull request! LGTM!

Any chance you could also add a sample file for .bro while you're at it?

[jsiwek]

@pchaigno Thanks, I added a sample .bro, but it's just identical to one of the .zeek samples. Let me know if a unique file (or even symlink) is preferred.

[pchaigno]

Thanks. Having duplicate sample files is indeed very likely to skew the Bayesian classifier. If you can find a .bro file under permissive license that would be better. If you can't it's not a big issue, we can just continue without .bro samples.

[jsiwek]

Ok, added a different .bro file. Source file and license.

[pchaigno]

Perfect! Thanks!