Made the test and benchmark library compile.

Both liblfds and libtest_and_benchmark (libtab for short) have subsets of libstds (library single threaded data structures) in.

Originally and wrongly I was expanding the subset in liblfds, where those data structures were being used by libtab. Now I have only the data structures needed by liblfds in liblfds, and only those needed by libtab in libtab.

I now need to move libtab fully away from using liblfds to using libstds.

It was a blunder to have used liblfds, because liblfds provides data structures to the extent you have atomic support, which means you might not have a list, for example – but libtab uses the list everywhere.

Actually maintaining this portability behaviour in the code is a lot of work. If I just assumed x64-level atomics, the portability code would go away. In a sense it matters, because the portability code right now is untested. I do not – and I will need to – build variants which pretend to have less support. With software if it’s not tested, it doesn’t work.