decoupled: make test_dec2p2cproblem compile, fix include of...

decoupled: make test_dec2p2cproblem compile, fix include of "defaultcomponents.hh" in old_fluidsystems/h2o_n2_system.hh

git-svn-id: svn://svn.iws.uni-stuttgart.de/DUMUX/dumux/trunk@7107 2fb0f335-1f38-0410-981e-8018bf24f1b0