On clang-7 with libc++ this results in a small error for the imaginary
unit which gets computed as `I = (-4.37114e-08,1)`.  This results in a
too large error in the tests.

Closes: #51

Merge branch 'bugfix/fix-vbv-create-iterator' into 'master'

ref:core/dune-istl When the postfix increment operator is used, block sizes
will not be set properly, see [#56].

This implementation places the allocation into the destructor of the iterator.

It does not need additional structures.

This MR also fixes the test for interoperability with STL algorithms: As the
CreateIterator is only an output iterator, use std::fill_n() instead of
std::fill().

See [!249]. Fixes [#56].

See merge request [!250]

  [#56]: gitlab.dune-project.org/NoneNone/issues/56
  [!249]: gitlab.dune-project.org/NoneNone/merge_requests/249
  [!250]: gitlab.dune-project.org/core/dune-istl/merge_requests/250


Closes #56

Tunnel size access of the CreateIterator through a proxy to work around interface limitations in the window type

See issue #56.

std::fill() requires a forward iterator, so don't use that algorithm.

Merge branch 'ci/centralize-config' into 'master'

See merge request [!248]

  [!248]: Nonecore/dune-istl/merge_requests/248

Merge branch 'feature/cleanup-dotproducttest' into 'master'

ref:core/dune-istl

-   Use Dune::Std::negation to negate meta function
-   Indent Dune::Hybrid::ifElse branch for better readability

See merge request [!247]

  [!247]: gitlab.dune-project.org/core/dune-istl/merge_requests/247

Merge branch 'feature/cleanup-cholmod' into 'master'

ref:core/dune-istl

-   Avoid a sign/unsigned comparison warning
-   Don't use C's unqualifies size_t
-   Use std::size_t in 0,...,k-1 loop

See merge request [!246]

  [!246]: gitlab.dune-project.org/core/dune-istl/merge_requests/246

* Use Dune::Std::negation to negate meta fuction
* Indent Dune::Hybrid::ifElse branch for better readability

* Avoid a sign/unsigned comparison warning
* Don't use C's unqualifies size_t
* Use std::size_t in 0,...,k-1 loop

Merge branch 'allow-blockvector-of-doubles' into 'master'

ref:core/dune-istl So, for example, you can write

    BlockVector<double>

instead of

    BlockVector<FieldVector<double,1> >

and it will do what you expect it to do. With this patch, any type for which
Dune::IsNumber<T>::value returns true will end the recursion.

See merge request [!240]

  [!240]: gitlab.dune-project.org/core/dune-istl/merge_requests/240

Feel free to put the test back in if it does serve a purpose
that I missed.  But please, if you do so please add an
explanation.

The BlockVector capacity is expected to be an unsigned integer.
However, literals like '100' are signed, and therefore triggered
a warning.

So, for example, you can write

  BlockVector<double>

instead of

  BlockVector<FieldVector<double,1> >

and it will do what you expect it to do.

Merge branch 'fix/solvers-doxygen-comments' into 'master'

ref:core/dune-istl Some \bief -\> \brief, @joe

See merge request [!244]

  [!244]: gitlab.dune-project.org/core/dune-istl/merge_requests/244

Merge branch 'fix-small-copy-n-paste-bugs' into 'master'

See merge request [!243]

  [!243]: Nonecore/dune-istl/merge_requests/243

This fixes what looks like a copy-n-paste bug.

Merge branch 'feature/mtbv-inherit-tuple-constructors' into 'master'

ref:core/dune-istl

-   Makes member function count const
-   Inherits tuple constructors so that MultiTypeBlockVector can be
    constructed from existing Vectors, or we can even construct it with
    references to existing vectors.
-   Test construction from references in the test
-   Fixes the static_assert in the test that shouldn't really have compiled
    before

See merge request [!241]

  [!241]: gitlab.dune-project.org/core/dune-istl/merge_requests/241

Merge branch 'fix-signed-unsigned-warning' into 'master'

See merge request [!239]

  [!239]: Nonecore/dune-istl/merge_requests/239

Merge branch '55-amg-set-hasDiagonal-to-true' into 'master'

ref:core/dune-istl Thanks to Nils-Arne Dreier for noticing.

Closes: [#55]

See merge request [!236]

  [#55]: gitlab.dune-project.org/NoneNone/issues/55
  [!236]: gitlab.dune-project.org/core/dune-istl/merge_requests/236


Closes #55