patch applied (ghc-6.6/ghc): MERGED: Establish the CoreSyn let/app invariant

[Ian Lynagh]

Fri Mar 16 18:12:22 PDT 2007  Ian Lynagh <igloo at earth.li>
  * MERGED: Establish the CoreSyn let/app invariant
  simonpj at microsoft.com**20070205173150

    M ./compiler/coreSyn/CoreUtils.lhs -16 +5
    M ./compiler/deSugar/DsExpr.lhs -7 +5
    M ./compiler/deSugar/DsUtils.lhs -4 +36