code: public static void addCol(Matrix A, int j, double c)
      {
          addCol(A, j, 0, A.rows(), c);
      }
docs: Updates the values of column <tt>j</tt> in the given matrix to be A[:,j] = A[:,j]+ c
  
  @param A the matrix to perform he update on
  @param j the row to update
  @param c the constant to add to each element