patch applied (packages/base): Clarify how one hides Prelude.catch

[Don Stewart]

Sat Aug 26 05:43:46 PDT 2006  Don Stewart <dons at cse.unsw.edu.au>
  * Clarify how one hides Prelude.catch
  
  User feedback indicated that an example was required, of how to hide
  Prelude.catch, so add such an example to the docs
  

    M ./Control/Exception.hs -5 +13