Add dbus-cpp into contrib system to force patches for all gnu/linux
platforms that use this library.
The problem with this library, it is not longer active and lacks of
support on recent changes as the compatibility break with gcc-7.

Credits: patches provided by this commit come from Fedora dbug-c++
package sources.

Change-Id: Ib06a3ee750f9715cfedd6289405828e662e7da94
Reviewed-by: Olivier Soldano <olivier.soldano@savoirfairelinux.com>