Log Message:
gsl: update to 2.7.

* What is new in gsl-2.7:

** fixed doc bug for gsl_histogram_min_bin (lhcsky at 163.com)

** fixed bug #60335 (spmatrix test failure, J. Lamb)

** fixed bug #36577

** clarified documentation on interpolation accelerators (V. Krishnan)

** fixed bug #45521 (erroneous GSL_ERROR_NULL in ode-initval2, thanks to M. Sitte)

** fixed doc bug #59758

** fixed bug #58202 (rstat median for n=5)

** added support for native C complex number types in gsl_complex
   when using a C11 compiler

** upgraded to autoconf 2.71, automake 1.16.3, libtool 2.4.6

** updated exponential fitting example for nonlinear least squares

** added banded LU decomposition and solver (gsl_linalg_LU_band)

** New functions added to the library:
      - gsl_matrix_norm1
      - gsl_spmatrix_norm1
      - gsl_matrix_complex_conjtrans_memcpy
      - gsl_linalg_QL: decomp, unpack
      - gsl_linalg_complex_QR_* (thanks to Christian Krueger)
      - gsl_vector_sum
      - gsl_matrix_scale_rows
      - gsl_matrix_scale_columns
      - gsl_multilarge_linear_matrix_ptr
      - gsl_multilarge_linear_rhs_ptr
      - gsl_spmatrix_dense_add (renamed from gsl_spmatrix_add_to_dense)
      - gsl_spmatrix_dense_sub
      - gsl_linalg_cholesky_band: solvem, svxm, scale, scale_apply
      - gsl_linalg_QR_UD: decomp, lssolve
      - gsl_linalg_QR_UU: decomp, lssolve, QTvec
      - gsl_linalg_QR_UZ: decomp
      - gsl_multifit_linear_lcurvature
      - gsl_spline2d_eval_extrap

** bug fix in checking vector lengths in gsl_vector_memcpy (dieggsy@pm.me)

** made gsl_sf_legendre_array_index() inline and documented
   gsl_sf_legendre_nlm()