Log Message:
gsl: update to 2.6.

* What is new in gsl-2.6:

** add BLAS calls for the following functions:
     - gsl_vector_memcpy
     - gsl_vector_scale
     - gsl_matrix_memcpy
     - gsl_matrix_transpose_memcpy
     - gsl_matrix_tricpy
     - gsl_matrix_transpose_tricpy

** deprecated functions gsl_linalg_complex_householder_hm and
   gsl_linalg_complex_householder_mh

** add unit tests for gsl_linalg_symmtd and gsl_linalg_hermtd

** multilarge TSQR algorithm has been converted to use the new Level 3 QR \ 
decomposition

** nonlinear least squares Cholesky solver now uses the new Level 3 BLAS
   method; the old modified Cholesky solver is still available under
   gsl_multifit_nlinear_solver_mcholesky and gsl_multilarge_nlinear_solver_mcholesky

** implemented Level 3 BLAS versions of several linear algebra routines:
     - Triangular matrix inversion
     - Cholesky decomposition and inversion (real and complex)
     - LU decomposition and inversion (real and complex)
     - QR decomposition (courtesy of Julien Langou)
     - Generalized symmetric/hermitian eigensystem reduction to standard form

** removed deprecated function gsl_linalg_hessenberg()

** renamed gsl_interp2d_eval_e_extrap() to gsl_interp2d_eval_extrap_e()
   to match documentation (reported by D. Lebrun-Grandie)

** renamed some of the gsl_sf_hermite functions to be more consistent
   with rest of the library, and deprecated old function names

** updated gsl_sf_hermite_func() to use a newer algorithm
   due to B. Bunck which is more stable for large x; also added
   gsl_sf_hermite_func_fast() which uses the faster Cauchy integral
   algorithm in the same paper by Bunck

** add gsl_vector_axpby()

** add un-pivoted LDLT decomposition and its banded
   variant (gsl_linalg_ldlt_* and gsl_linalg_ldlt_band_*)

** add binary search tree module (gsl_bst); based on GNU libavl

** remove -u flag to gsl-histogram

** updated spmatrix module
   - added routines and data structures for all types (float,uint,char,...)
   - added gsl_spmatrix_scale_columns() and gsl_spmatrix_scale_rows()
   - added gsl_spmatrix_add_to_dense()
   - more efficient reallocation of COO/triplet matrices (no longer rebuilds \ 
binary tree)
   - enhanced test suite
   - added gsl_spmatrix_min_index()

** add routines for banded Cholesky decomposition (gsl_linalg_cholesky_band_*)

** documented gsl_linalg_LQ routines and added gsl_linalg_LQ_lssolve()