[release] Remove unused local typedefs.
(cherry picked from commit c011932927d3f7ebb480ec1831dbd8c5bd3f0c29)

Signed-off-by: Christoph Grüninger <gruenich@dune-project.org>
[release][autotools] Add warning about deprecation of module dune-grid-dev-howto.
(cherry picked from commit c695f2e4cb52f1364eeac1480393093a8fd428a6)

Signed-off-by: Christoph Grüninger <gruenich@dune-project.org>
[release] Update list of copyright holders until Dune 2.3.
(cherry picked from commit b0ecb5d14186abd634f1ccb295b97d1f6795f931)

Signed-off-by: Christoph Grüninger <gruenich@dune-project.org>