patch applied (packages/base): Generalise the type of synthesize, as suggested by Trac #1571

[Simon Peyton Jones]

Wed Aug  1 05:52:08 PDT 2007  simonpj at microsoft
  * Generalise the type of synthesize, as suggested by Trac #1571
  
  I have not looked at the details, but the type checker is happy with the
  more general type, and more general types are usually a Good Thing.
  

    M ./Data/Generics/Schemes.hs -1 +1