[Release][MPI] Add check for MPI standard version and warn if installed version is < 2.1

As decided in the doodle for FS#1395, really old MPI versions will be
deprecated in the 2.3 release.

This patch adds an additional check to the MPI tests for autotools and
cmake that makes sure the user has an MPI which is at least compliant
with MPI-2.1. If the user's version is older, a warning is generated.

The test uses version macros instead of the more standard runtime
MPI version query interface to avoid problems when cross-compiling.
(cherry picked from commit ac6885f8af7c6b63e99f3285ef2a98d2c5523637)

Signed-off-by: Christoph Grüninger <gruenich@dune-project.org>
[release][autotools] Fix man page inclusion.

This fixes make dist.
(cherry picked from commit 3bf1f921ed512516ac2222ffc1b4072b20ff76b1)

Signed-off-by: Christoph Grüninger <gruenich@dune-project.org>
[parallel,release] Removed superfluous typedef and documented another one in Interface.
(cherry picked from commit 6c77b15990caa37f936f73301091ebec20c51171)

Signed-off-by: Christoph Grüninger <gruenich@dune-project.org>
[parallel,release] Adds a new buffered communicator that does not need to know the data amount per index when receiving.

During communication of data with a parallel DUNE grid the amount of data items
received at an index is not known at the receiving side. With this communicator
it is possible to build such a communication based on index lists at the sending
and receiving side. With this patch only fixed size of data items per index is
supported.
(cherry picked from commit dd1e859555ec3d34e7aea5df940e1f08c129b41d)

Signed-off-by: Christoph Grüninger <gruenich@dune-project.org>
[parallel,release] Added implementation for the case of varying number of data per index.

With this patch VariableSizeCommunicator now really supports a varying number of data entries
per index during communication.
(cherry picked from commit 8ce0663426e4574f238d0239511a6bbb2df0d04c)

Signed-off-by: Christoph Grüninger <gruenich@dune-project.org>
[parallel,release] Removes dead code and makes test compile again.
(cherry picked from commit b9773dee43fed3de637705e728dd4e5c063f86c8)

Signed-off-by: Christoph Grüninger <gruenich@dune-project.org>
[release] Removes unused parameter warnings with -Wall -Wextra
(cherry picked from commit e5ca9a37f6d7d6432c7219e85875844c60056cd2)

Signed-off-by: Christoph Grüninger <gruenich@dune-project.org>
[release] Update list of copyright holders until Dune 2.3.
(cherry picked from commit 9f1a1126b2fb2ea540882fd7c1391ec4b9d7beaf)

Signed-off-by: Christoph Grüninger <gruenich@dune-project.org>
[buildsystem] distribute cxx11_constexpr.m4

The check for constexpr was not copied into the distribution.
Unfortunately, the autotools will only warn about a missing macro, but
give valid results otherwise. This patch adds the cxx11_constexpr.m4 to
Makefile.am, so that it is distributed on "make dist".
(cherry picked from commit 3887555aa286141b1476fde7ad98ebf0217e2805)

Signed-off-by: Christoph Grüninger <gruenich@dune-project.org>
[CMake] Add missing CMake files to release tarball.
(cherry picked from commit 6701492a340edce663addbb25967cfd50e94f1c2)

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