AutoPolicy can take a handler argument to use a different Handler.
The default Handler class now uses GLib's mainloop. This should make integration
with an existing mainloop easier, and opens up the possibility for timeouts, etc.
Handler.wait_for_downloads() now uses a GLib mainloop. One minor effect of this is
that errors during downloading are now reported by calling report_error(), not by
throwing the exception from wait_for_downloads.
git-svn-id: file:///home/talex/Backups/sf.net/Subversion/zero-install/trunk/0launch@1923 9f8c893c-44ee-0310-b757-c8ca8341c71e