Updating net/deskflow - #include <format> and doxygen issues

[David Brownlee <abs%absd.org@localhost>]

I noticed that net/deskflow didn't build for me - turns out if doxygen
is installed it unconditionally tries to build its docs.

There was an existing "-DBUILD_DOCS=OFF" attempt to disable the docs,
but should we be trying to build it with these (user, not dev) docs?

I looked at updating to the next version, but it now uses '#include
<format>' which looks to be a c++20 feature... but pkgsrc allows gcc12
for c++20... which does not include support for <format>

So, we could
- Add GCC_REQD=13 to force a version of gcc that supports <format>
- Patch the package to not need <format> (There is already an
__APPLE__ path that avoids it)
- Other?

WIP diff at https://sync.absd.org/pkgsrc/deskflow.diff

Thanks

David