Log Message:
Updated gsl to 2.4.

* What is new in gsl-2.4:

** migrated documentation to Sphinx software, which has built-in
   support for latex equations and figures in HTML output

** add const to declaration of appropriate gsl_rstat routines

** bug fix for #45730: change gsl_sf_sin/cos to libm sin/cos

** fix Cholesky documentation regarding upper triangle on output

** added routines to compute integrals with fixed-point quadrature,
   based on IQPACK (Konrad Griessinger)

** added routines for Hermite polynomials, gsl_sf_hermite_*
   (Konrad Griessinger)

** added new nonlinear least squares example for fitting
   a Gaussian to data

** deprecated routines:
     gsl_sf_coupling_6j_INCORRECT
     gsl_sf_coupling_6j_INCORRECT_e

** deprecated routine 'gsl_linalg_hessenberg' (replaced
   by gsl_linalg_hessenberg_decomp)

** removed routines which were deprecated in v2.1:
     gsl_bspline_deriv_alloc
     gsl_bspline_deriv_free

** changed COD expression to Q R Z^T instead of Q R Z to
   be consistent with standard texts

** added check for nz == 0 in gsl_spmatrix_get
   (reported by Manuel Schmitz)

** permit zero-dimension blocks, vectors, matrics, subvectors,
   submatrices, and views of the above (bug #49988)

** added routine gsl_linalg_COD_lssolve2 for regularized
   least squares problems