Update / benchmarking 7.0.0

Documentation first-pass finished.

No missing articles.

I need to fix up the “enum flag” type use in the codebase – there’s a type in liblfds itself, and another in the test_and_benchmark code, and they’re intermixed in that code. It needs to be one or the other.

Changing subject, the code for each release of liblfds is wholly indpendent and occupies different namespaces (by means of prefixes to the names of all public entities). As such, every version of the library can be compiled against and linked to, concurrently.

As such, the benchmark app can benchmark *the different versions of the same data structure*.

I’ve just spent an hour adding in a benchmark for the 7.0.0 btree!

The performance is really bad, though – and I never remembered it being like this; it was also pretty good. So I’m wondering if I’ve flubbed up the implementation somewhere along the line.