[AlignedNumber] Run the SIMD testsuite.

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>&&`).

dune/common/debugalign.hh

@@ -460,7 +460,7 @@ namespace Dune {
       }
 
       template<class T, std::size_t align>
-      const T& lane(ADLTag<5>, std::size_t l, const AlignedNumber<T, align> &v)
+      T lane(ADLTag<5>, std::size_t l, const AlignedNumber<T, align> &v)
       {
         assert(l == 0);
         return v.value();

dune/common/test/CMakeLists.txt

@@ -77,6 +77,10 @@ dune_add_test(SOURCES debugaligntest.cc
               LINK_LIBRARIES dunecommon
               LABELS quick)
 
+dune_add_test(SOURCES debugalignsimdtest.cc
+              LINK_LIBRARIES dunecommon
+              LABELS quick)
+
 dune_add_test(SOURCES densematrixassignmenttest.cc
               LINK_LIBRARIES dunecommon
               LABELS quick)

dune/common/test/debugalignsimdtest.cc

+#include <config.h>
+
+#include <cstdlib>
+
+#include <dune/common/debugalign.hh>
+#include <dune/common/parallel/mpihelper.hh>
+#include <dune/common/simd/test.hh>
+
+int main(int argc, char **argv)
+{
+  Dune::MPIHelper::instance(argc, argv);
+
+  Dune::Simd::UnitTest test;
+
+  test.checkVector<Dune::AlignedNumber<double> >();
+
+  return test.good() ? EXIT_SUCCESS : EXIT_FAILURE;
+}