/usr/include/signond/ is in signond-dev 8.58+16.04.20151106-0ubuntu1.
This file is owned by root:root, with mode 0o755.
..
/usr/include/signond/accesscontrolmanagerhelper.h
/usr/include/signond/backupifadaptor.h
/usr/include/signond/credentialsaccessmanager.h
/usr/include/signond/credentialsdb.h
/usr/include/signond/credentialsdb_p.h
/usr/include/signond/default-crypto-manager.h
/usr/include/signond/default-key-authorizer.h
/usr/include/signond/default-secrets-storage.h
/usr/include/signond/pluginproxy.h
/usr/include/signond/signonauthsession.h
/usr/include/signond/signonauthsessionadaptor.h
/usr/include/signond/signoncommon.h
/usr/include/signond/signond-common.h
/usr/include/signond/signondaemon.h
/usr/include/signond/signondaemonadaptor.h
/usr/include/signond/signondisposable.h
/usr/include/signond/signonidentity.h
/usr/include/signond/signonidentityadaptor.h
/usr/include/signond/signonidentityinfo.h
/usr/include/signond/signonsessioncore.h
/usr/include/signond/signonsessioncoretools.h
/usr/include/signond/signontrace.h
/usr/include/signond/signonui_interface.h