…a source in install targets.

- Something I've been meaning to do for far too long now is make the GDB pretty printers
auto-loading so you don't have to set up `.gdbinit`. This is now done. I also improved
the pretty printers to also pretty print the C result type which can be very useful if
working with that type, as it will print the error message in GDB.

 Experimental Outcome's `status_code` has also gained its own auto-loading GDB pretty printer
with display of `strerror()` if the code domain is POSIX or generic.

CI fixes

Hopefully fix issue #300 caused by MSVC changing what diagnostic
it prints.

Fix issue #299 GCC 14 warns on use of `_`.

…inning, however it had

been mainly intended that C++ would originate Results, they would pass through C, and back
into C++. It hadn't really been expected that C would want to do much with Results other than
inspect them for happy or sad path.

 It turns out there is more demand than expected for a more functional Result from within C,
so this release adds the power to create Results in success and two types of failure, semantic
comparison of Results, and printing of Result messages. You can also wrap a C enum into a
quick status code from enum, allowing easy custom C error coding from 100% within C.

 [The documentation for the C support]({{% relref "../experimental/c-api" %}}) has been updated
to reflect the new facilities.

- Outcome.Experimental has had C representation support since the beginning, however it had
been mainly intended that C++ would originate Results, they would pass through C, and back
into C++. It hadn't really been expected that C would want to do much with Results other than
inspect them for happy or sad path.

 It turns out there is more demand than expected for a more functional Result from within C,
so this release adds the power to create Results in success and two types of failure, semantic
comparison of Results, and printing of Result messages. You can also wrap a C enum into a
quick status code from enum, allowing easy custom C error coding from 100% within C.

 [The documentation for the C support]({{% relref "../experimental/c-api" %}}) has been updated
to reflect the new facilities.

Add missing docs for previous commit.

…ation.

Fixes to previous commits as found the code didn't link under optimisation.

…ation.

Fixes to previous commits as found the code didn't link under optimisation.

…ation.

Fixes to previous commits as found the code didn't link under optimisation.

…ation.

Fixes to previous commits as found the code didn't link under optimisation.

…targets.