Issue #17269: Workaround for a platform bug in getaddrinfo on OSX

Without this patch socket.getaddrinfo crashed when called
with some unusual argument combinations.
Issue #17953: document that sys.modules shouldn't be replaced (thanks
to interp->modules) and that deleting essential items from the dict
can cause Python to blow up.

Thanks to Terry Reedy for coming up with initial wording and Yogesh
Chaudhari for coming up with a patch using that wording in parallel to
my own patch.
indicate that read/write work with bytes (closes #18009)