Usage: <tt>input = [ <i> M11 M12 M13 M21 M22 M23 M31 M32 M33 <br>
  &nbsp;  &nbsp;  &nbsp;  &nbsp; s11 s12 s13 s21 s22 s23 s31 s32 s33 <br>
  &nbsp;  &nbsp;  &nbsp;  &nbsp; eps </i> ] </tt>

<p>
Apply a strain to box matrix <tt>H</tt> while keeping the scaled coordinates
of the atoms fixed.  The first nine components of the <tt>input</tt> array
specify the transformation matrix <tt><b>M</b></tt>, the next nine components specify
the strain matrix <tt><b>EPSILON</b></tt> in a rotated coordinate system.  The
row vectors of matrix <tt><b>M</b></tt> are normalized by MD++ if they were not
already normalized in the input.

<p>
<tt><b>H</b> += <b>M</b> * <b>EPSILON</b> * <b>M</b><sup>T</sup> * eps </tt>

<p>
The box matrix prior to applying the strain is saved into <tt>H0</tt>.

