[SIMD/test] Do not access indeterminate simd vectors with lane().

See merge request !519

Depending on implementation, this may require bitmask operations on the
indeterminate value, which requires an lvalue-to-rvalue conversion, which
results in undefined behaviour except in some very special cases.

Add helper function unpackIntegerSequence

See merge request !495

[SIMD] Test the index vectors the same way we test other vectors.

Closes #125

See merge request !516

In the tests for operations we check whether an operation is supported on
scalars, and if so, we also test is in simd types.  This suppresses tests for
e.g. `%` on simd types made up of floating point types.  Before this patch we
sometimes did the check on proxies instead of scalars.  This could lead to
tests be incorrectly not suppressed.

This had been watered down because vectorclass does not implement some
functionality for integer vector types (like certain forms of division or
bitshift).

Instead of watering down the test, we're now going to provide that
functionality in a poor efficiency version.

[SIMD] Get rid of IsStandard and all specializations.

Closes #122

See merge request !514

Fixes: #122.

A non-const class rvalue is, in fact, assignable, unless you take special
care.  In the tests we try to apply each operator to `Scalar<V>` in an
unevaluated context, and if that succeeds we require that it works for `V`
analogously to how it does for `Scalar<V>`.

That heuristic fails if `Scalar<V>` is a class (such as `std::complex`),
because assignment works even to rvalues (usually), but trying to apply the
assignment to a `V` rvalue and then capturing and examining the result will
lead to undefined behaviour.

[AlignedNumber] Run the SIMD testsuite.

Closes #123

See merge request !511

[ArithmeticTestSuite] Inherit constructors from TestSuite.

See merge request !512

This makes it possible to e.g. attach a name to the testsuite object.

Also run the simd testsuite on AlignedNumber, sind it does provide a SIMD
abstraction.

Also fixes one issue with that abstraction (though I do not recall why exactly
I did not allow `const Scalar<T> &lane(T &&)`, but required the return type to
be one of `Scalar<T>` or `Scalar<T>&&`).

[Simd::IsStandard] Disable for AlignedNumber too.

See merge request !510

This fixes the tests for istl again.

See !509, #122.

[Simd::IsStandard] Disarm.

Closes #121

See merge request !509

Fixes: #121.

Stop-gap measure to to accept any type in the adaption for standard types.

Minor moderization of pool allocator

See merge request !507

Also use a `std::vector` instead of plain `new[]` and `delete[]`.

[CI] Only run quick tests by default.

See merge request !502

[SIMD] let LoopSIMD use the mathclassifier interface

See merge request !498

[doc] add docstring to `e` and `pi` [ci skip]

See merge request !506

They don't appear in the Doxygen documentation otherwise.

Simplify mathematical constants

See merge request !505

removed the specialization of MathematicalConstants as the generic class MathematicalConstants<Field> already covers these use cases

DuneMPI: add spaces around linker flags

See merge request !503

[Ninja] Fix build system self-destructing on clean

Closes #119

See merge request !501

Same reasoning as 4063acee applies,
however there is no LINK_OPTIONS that could be used instead of
LINK_FLAGS [1].  So just add some spaces to make sure that distinct
options aren't joined by accident.

  [1]: https://gitlab.kitware.com/cmake/cmake/issues/16543

List generated files including `CMAKE_CURRENT_BINARY_DIR` in
`DUNE_INSTANCE_GENERATED`.  This means we do not need to set the source file
property `GENERATED` on the generated files, which is only meant for files
generated during build time (e.g. with `add_custom_command()` or during
generate time (e.g. with `file(GENERATE)`).

Closes: #119

DuneMPI: append flags to `COMPILE_OPTIONS` instead of `COMPILE_FLAGS`

See merge request !499

`COMPILE_FLAGS` is a string, but `set_property(... APPEND ...)`
appends to a list.  If the list of compile flags is not empty this
results in a superfluous semicolon in the compile flags which will
break the compiler invocation.

For example, when `MPI_DUNE_COMPILE_FLAGS=-lpthread`, calling
`add_dune_mpi_flags` twice for the same target would result in the
compiler command containing `-lpthread;-lpthread`.

This patch makes use of the `COMPILE_OPTIONS` property instead which
is a list.