patch applied (cabal): install headers for all compilers

[Duncan Coutts]

Fri Apr 20 05:35:27 PDT 2007  Bertram Felgenhauer <int-e at gmx.de>
  * install headers for all compilers
  This patch moves the installation of header files from Distribution.Simple.GHC
  to Distribution.Simple.Install. This is required for the header files to be
  usable for preprocessing Haskell code in other packages.

    M ./Distribution/Simple/GHC.hs -23 +1
    M ./Distribution/Simple/Install.hs -4 +30