[cleanup] make headercheck compile.

cmake/modules/TargetDistclean.cmake

dune.module

dune/fem-dg/algorithm/gridinitializer.hh

dune/fem-dg/algorithm/handler/additionaloutput.hh

dune/fem-dg/misc/error/dgeocerror.hh

dune/fem-dg/misc/error/h1eocerror.hh

dune/fem-dg/misc/error/l1eocerror.hh

dune/fem-dg/misc/error/l2eocerror.hh

dune/fem-dg/misc/parameterkey.hh

dune/fem-dg/misc/problemcreatorselector.hh

dune/fem-dg/misc/simulator.hh

dune/fem-dg/misc/tupleconcat.hh

dune/fem-dg/operator/dg/fluxoperator.hh

dune/fem-dg/operator/fluxes/llfadvflux.hh

dune/fem-dg/operator/fluxes/upwindflux.hh

dune/fem-dg/solver/uzawa.hh

dune/fem-dg/test/advdiff/parameter

dune/fem-dg/test/combined/parameter

dune/fem-dg/test/dataio/parameter

dune/fem-dg/test/euler/parameter