Some API deprecation -- ExperimentalAgc and ExperimentalNs are gone.
We're continuing to carry iSAC even though it's gone upstream, but maybe
we'll want to drop that soon.
* Rename Windows.h uses to windows.h
* Comment out structured exception handling usage
Makes MinGW happier. Mostly the same as previous work by
Nicolas Dufresne <nicolas.dufresne@collabora.com>, with the exception
that we now don't try to invoke RaiseException which would fail in MinGW
as it raises a Windows structured exception.