Out of date chunks in documentation

[Hal Murray]

> One way we can dodge around this is by changing those assertions to "version
> X and later".  Forward-compatibility breaks affecting the stuff we use are so
> rare that I think this is safe - and on thoe exceotional occasions they cause
> enough ruckus that we are unlikely not to notice. 

That ends up claiming support for old versions.  We could easily clean up 
something that would break an old version and not notice it because we weren't 
actively testing that version.

Consider the recent timer_create.  It got past all the CI tests.  If Apple had 
fixed that area and we didn't test on an old/broken version of macOS we never 
would have noticed.


-- 
These are my opinions.  I hate spam.