matmul is depreceated and replaced by matmul_v2 ()
Important to note that many routines were using matmul which is now a private case of matmul_v2 (which is renamed)
test added to check_lsqadj.c is showing the way to use the new matmul : add two integers at the end of the arguments, identical to the
first integers, i.e. set m_large == m and n_large == n