external: Update openconnect to jni-v5 branch
libs: Sync openconnect with latest sources

Signed-off-by: Kevin Cernekee <cernekee@gmail.com>
AuthFormHandler: Add NEWGROUP support

Return to libopenconnect when the user clicks a different authgroup,
so that the server can re-render the form if necessary.  Use the info
provided by the library (FormChoice.selected) to determine which item
to show as active in the dialog.

Signed-off-by: Kevin Cernekee <cernekee@gmail.com>
AuthFormHandler: Automatically select saved authgroup from preferences

On the first pass through, allow AuthFormHandler to set the authgroup
non-interactively before the user sees the auth dialog.

Signed-off-by: Kevin Cernekee <cernekee@gmail.com>
UserDialog: Implement deferred preferences

Save the auth form preferences to a local HashTable and avoid writing
them out to flash until we've successfully authenticated.  This prevents
saving mistyped usernames/passwords or other bad data.

Signed-off-by: Kevin Cernekee <cernekee@gmail.com>