Implement boolean reductions for zero-sized objects
C++11: add template metaprogramming helpers

Create a new directory CXX11 under unsupported/Eigen that contains code
that requires C++11. In that directory, add a few generic templates
useful for any module relying on C++11. These templates may be included
with #include <[unsupported/]Eigen/CXX11/Core>. At the moment, this
will only provide templates in the Eigen::internal namespace.
CXX11/Tensor: add simple initial tensor implementation

This commit adds an initial implementation of a class template Tensor
that allows for the storage of objects with more than two indices.
Currently, only storing data and setting the object to zero for POD
data types are implemented.
CXX11/TensorSymmetry: add symmetry support for Tensor class

Add a symCoeff() method to the Tensor class template that allows the
user of the class to set multiple elements of a tensor at once if they
are connected by a symmetry operation with respect to the tensor's
indices (symmetry/antisymmetry/hermiticity/antihermiticity under
echange of two indices and combination thereof for different pairs of
indices).

A compile-time resolution of the required symmetry groups via meta
templates is also implemented. For small enough groups this is used to
unroll the loop that goes through all the elements of the Tensor that
are connected by this group. For larger groups or groups where the
symmetries are defined at run time, a standard run-time implementation
of the same algorithm is provided.

For example, the following code completely initializes all elements of
the totally antisymmetric tensor in three dimensions ('epsilon
tensor'):

SGroup<3, AntiSymmetry<0,1>, AntiSymmetry<1,2>> sym;
Eigen::Tensor<double, 3> epsilon(3,3,3);
epsilon.setZero();
epsilon.symCoeff(sym, 0, 1, 2) =  1;
fix overflow and ambiguity in SparseLU memory allocation
Workaround fixing aliasing issue in x = SparseLU::solve(x)
C++11/Tensor: Fix copyright headers
Merged in chris-se/eigen/tensor-for-merge (pull request #39)

Tensor support for Eigen
Document how to reproduce matlab's rot90
Add scaling in JacobiSVD to avoid overflows
Fix FullPivHouseholderQR ctors for non squared fixed size matrix types
extend Map unit test to check buffers allocated on the stack
Fix bug 708: add placement new/delete for array
Fix Bug 609: Euler angles are in Range [0:pi]x[-pi:pi]x[-pi:pi].
Now the unit test verifies this (also that it is bijective in this range).
Fixed and simplified Matlab code and added further block-related examples