While gcc supports them (as extension) runtime sized arrays
are not standard c++. They are not even contained in c++14
but postponed to a later TS.

Rather than assuming the caller has set it to the correct size already.
Setting the size in the method eigenValuesNonSym itself makes code
more robust.  Plus, the time needed for that should be negligible
compared to the actual eigenvalue computations.

[[Imported from SVN: r7431]]

[[Imported from SVN: r7430]]

[[Imported from SVN: r7093]]

[[Imported from SVN: r7062]]

Capabilities to compute eigenvalues on non-symmetric matrices
Code contributed by Arne Morten Kvarving.

[[Imported from SVN: r7061]]