That should be no problem now that we use a 50-decimal digits type
for the FD approximation.

[[Imported from SVN: r9876]]

[[Imported from SVN: r9875]]

It offers a 'double' interface, but we don't really need that.

[[Imported from SVN: r9874]]

[[Imported from SVN: r9873]]

[[Imported from SVN: r9872]]

[[Imported from SVN: r9870]]

This code compares scalar and vector AD, and a finite difference
approximation.

[[Imported from SVN: r9869]]

[[Imported from SVN: r9681]]

[[Imported from SVN: r9680]]

[[Imported from SVN: r9614]]

[[Imported from SVN: r9573]]

[[Imported from SVN: r9436]]

This still fails -- there must still be a bug in the Hessian computation

[[Imported from SVN: r9427]]

[[Imported from SVN: r9420]]

[[Imported from SVN: r9419]]

Hence many input configurations are tested now

[[Imported from SVN: r9418]]

They are easier to debug

[[Imported from SVN: r9417]]

[[Imported from SVN: r9416]]

[[Imported from SVN: r9413]]

[[Imported from SVN: r9411]]

[[Imported from SVN: r9410]]

[[Imported from SVN: r9409]]

[[Imported from SVN: r9408]]

[[Imported from SVN: r9407]]

[[Imported from SVN: r9406]]

[[Imported from SVN: r9382]]

[[Imported from SVN: r9377]]

[[Imported from SVN: r9289]]

[[Imported from SVN: r9288]]

[[Imported from SVN: r9287]]

[[Imported from SVN: r9198]]

[[Imported from SVN: r9197]]

And use it in the test.

This patch uses the new 'constexpr' macro.  Hence it is C++11 only.

[[Imported from SVN: r9195]]

[[Imported from SVN: r9188]]

[[Imported from SVN: r9186]]

[[Imported from SVN: r9077]]

[[Imported from SVN: r8871]]

[[Imported from SVN: r8870]]

properly implement getting the Lagrange nodes.  Works without a priori information for all orders and dimensions

[[Imported from SVN: r8869]]

[[Imported from SVN: r8868]]