NEWS tweak.

Avoid deprecation warning for `<ciso646>`. (#1027)

I was being too conservative in removing the use of this header.  True,
it was still a part of the standard in C++17.  But it was already
deprecated at that point!

Mark test registrars as `maybe_unused`. (#979)

Update config, reformat. (#913)

NEWS.

Disable clang-based parsing in Doxygen. (#847)

The clang-assisted parsing in Doxygen is supposed to be slower but more
accurate.

However I find that it just leads to tons of ridiculous errors, showing
a complete and radical lack of comprehension of the code it's parsing.
Seems to be failing to expand macros.

Typo in NEWS.

Update NEWS.

Introduce `std::source_location`. (#702)

Introduce `std::source_location`.

Allow exceptions to track source locations.  This is still pretty
rudimentary.

One thing I'm not happy about is the way different exception classes
have their own `source_location` members that are not related to each
other.  This means that if you want to access that field, you have to
catch a fairly specific exception type.

Also of course, it's not great that we can't assume that the compiler
actually supports this feature.  The testing helpers could be much nicer
if they could rely on `source_location` — we might even get by without
some of the preprocessor macros.

Regenerate.