Various cleanups: threads, STA_NANO

[Matthew Selsky]

On Wed, Jan 23, 2019 at 12:43:53AM -0500, Eric S. Raymond wrote:

> That's because our actual support target is this:
> 
>     This software should build on any operating system conformant to
>     POSIX.1-2001 and ISO/IEC 9899:1999 (C99).  In addition, the operating
>     system must have an ntp_adjtime(2) call. Also, it must support the
>     IPv6 API defined in RFC 2493 and RFC 2553. Finally, it must support
>     iterating over active UDP interfaces via getifaddrs(3) or some
>     equivalent facility.
> 
> There is some point in listing known-good platforms (Linux is the
> biggie), but no point in trying to be exhaustive about it, because
> anybody with enough chops to build this on a Unix variant we don't
> know about is necessarily clued in enough to apply this creterion
> themselves.

Agreed.  Can we update https://www.ntpsec.org/supported-platforms.html to be less specific to avoid having yet another table that we need to update?  We can list distros, since that won't change much.

> Maybe we want to replace that with "we support the current (and current - 1) versions of the following platforms/distros as long as they're supported by upstream"?  Or replace this section with a link to docs.ntpsec.org and the CI system?

If you're OK with some variation of this, I'll submit an MR.

Thanks,
-Matt