Sort numbers into complex conjugate pairs.

  Y = CPLXPAIR(X) rearranges the elements of vector X so that

  complex numbers are collected into matched pairs of complex

  conjugates.  The pairs are ordered by increasing real part.

  Any purely real elements are placed after all the complex pairs.

  Y = CPLXPAIR(X,TOL) uses a relative tolerance of TOL for

  comparison purposes.  The default is TOL = 100*EPSMO1RU2.