Recursive function used by QUAD8HSRNMC.

  [Q,cnt] = quad8stp(F,a,b,tol,lev,w,f,Q0) tries to approximate

  the integral of f(x) from a to b to within a relative error of tol.  

  F is a string containing the name of f.  The remaining arguments are 

  generated by quad8 or by the recursion.  lev is the recursion level.

  w is the weights in the 8 panel Newton Cotes formula.

  x0 is a vector of 9 equally spaced abscissa is the interval.

  f0 is a vector of the 9 function values at x.

  Q0 is an approximate value of the integral.

  See also QUAD8HSRNMC and QUAD1D3MCU2.