We can move past 1.44.2 now because:
* We no longer support compilers without C11 atomics.
* We can restore support for Windows 7 and macOS 10.x
ourselves, at least for the subset of libuv we need.
On other platforms libuv no longer supports, users can build
against an older external libuv.
libuv 1.45 and above have higher minimum requirements than we do.
Until we raise ours, we will have to stick with 1.44.2 and backport
any further changes we need.
Brad King
Ben Boeckel