1.2.38 `sm1.bfunction'
----------------------

sm1.bfunction(F)
     :   It computes the global b-function of F.

   Description:

     It no longer calls sm1's original bfunction. Instead, it calls
     asir "bfct".


Algorithm:

      M.Noro, Mathematical Software, icms 2002, pp.147-157.

   Example:
      sm1.bfunction(x^2-y^3);

