external: Use the official openconnect v6.00 release

Signed-off-by: Kevin Cernekee <cernekee@gmail.com>
libs: Sync with latest openconnect sources

Signed-off-by: Kevin Cernekee <cernekee@gmail.com>
Add XposedBridgeApi-54.jar to build

Signed-off-by: Kevin Cernekee <cernekee@gmail.com>
xposed: Add a module for bypassing the VpnService dialog

If a user has rooted their device and installed the Xposed framework,
an "OpenConnect" Xposed module will become available and this will allow
bypassing the system-managed VPN confirmation dialog.

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