patch applied (ghc): Make the loop-breaking algorithm a bit more liberal, where RULES are involved

[Simon Peyton Jones]

Mon Jan 21 05:56:54 PST 2008  simonpj at microsoft.com
  * Make the loop-breaking algorithm a bit more liberal, where RULES are involved
  
  This is another gloss on the now-quite-subtle and heavily-documented algorithm
  for choosing loop breakers.
  
  This fix, provoked by Roman's NDP library, makes sure that when we are choosing
  a loop breaker we only take into account variables free on the *rhs* of a rule
  not the *lhs*.
  
  Most of the new lines are comments!
  

    M ./compiler/simplCore/OccurAnal.lhs -4 +27