mfh 11 Sep 2015: The *_float128.cpp files in this directory do
explicit template instantiation (ETI) for Thyra classes.  Thyra uses
the TEUCHOS_CLASS_TEMPLATE_INSTANT_SCALAR_TYPES macro (defined in
teuchos/core/src/Teuchos_ExplicitInstantiationHelpers.hpp) for ETI.
This macro only instantiates over (at most) Scalar = float, double,
std::complex<float>, and std::complex<double>.  I could add __float128
to that list, but not every Thyra class builds with Scalar =
__float128 (for example, because Teuchos::LAPACK does not have a valid
implementation for that type).  Thus, in this directory, I have added
ETI for Scalar = __float128, for only the Thyra types that Ifpack2
needs in order to build its adapter.
