Log Message:
Update lang/ghc to 6.6.1.

Many, many bugs have been fixed relative to 6.6. Far too many to list here.

The other changes in this release are:
* GHC works on Windows Vista.
* GHC can now be used to compile C++ files.
* There is an --install-signal-handlers=<yes|no> RTS flag. The main use is
  to stop GHC installing signal handlers when you are putting your code in
   a DLL.
* Newtypes can now be defined using GADT syntax.
* Linear implicit parameters are no longer accepted.
* There is a manpage for ghc and ghci.
* The building guide has been moved to the wiki.
* GHC now comes with the filepath library.