First try at specfun

[ckormanyos]

See also related issue

[ckormanyos]

The specfun test runs locally, but does not pass. It does not run on the remote in CI for some reason.

At the moment, there are about 10-12 files failing with several types of failures including:

• over/underflow,
• bad exact-long-double-string-read
• and simple tolerance issues.

I'll check in this state anyway since the (non-running) specfun passes and further investigations can be carried out locally.