Minimal C++ routines for

• Polar decomposition of a 3x3 matrix
• 3x3 matrix SVD (Singular Value decomposition)
• Eigen decomposition (extract eigenvalues and eigenvectors) of a 3x3 matrix M (assumes symmetric matrix)

code inspired from Vega 3.0 originally under BSD license

    (http://run.usc.edu/vega/download.html)
    Jernej Barbič, Fun Shing Sin, Daniel Schroeder: 
     Vega FEM Library. 2012. http://www.jernejbarbic.com/vega

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