Massive speed improvement in sparse min/max functions for calls like 'max(s,[],2)' (bug #40268) * dSparse.cc (SparseMatrix SparseMatrix::max (Array<octave_idx-type>&, int)) : Remove triple loop by using a local buffer (SparseMatrix SparseMatrix::min (Array<octave_idx-type>&, int)) : ditto * CSparse.cc (SparseComplexMatrix SparseComplexMatrix::max ( Array<octave_idx-type>&, int)) : Remove triple loop by using a local buffer (SparseComplexMatrix SparseComplexMatrix::min (Array<octave_idx-type>&, int)) : ditto