Removed old extensible-exceptions, only needed for very old ghc.
Made webdav use Utility.Exception, to work after some changes in DAV's
exception handling.
Removed Annex.Exception. Mostly this was trivial, but note that
tryAnnex is replaced with tryNonAsync and catchAnnex replaced with
catchNonAsync. In theory that could be a behavior change, since the former
caught all exceptions, and the latter don't catch async exceptions.
However, in practice, nothing in the Annex monad uses async exceptions.
Grepping for throwTo and killThread only find stuff in the assistant,
which does not seem related.
Command.Add.undo is changed to accept a SomeException, and things
that use it for rollback now catch non-async exceptions, rather than
only IOExceptions.
For example, I had a copy to a remote that was failing for an unknown
reason. This let me see the exception was createDirectory: permission
denied; the underlying problem being a permissions issue.
Motivation: Hook scripts for nautilus or other file managers
need to provide the user with feedback that a file is being downloaded.
This commit was sponsored by THM Schoemaker.
