patch applied (ghc): move generic graph-colouring code into util

[Simon Marlow]

Wed Sep 12 04:41:10 PDT 2007  Simon Marlow <simonmar at microsoft.com>
  * move generic graph-colouring code into util
  It is needed by cmm/StackColor, and hence is needed even when there is no
  native code generator.

     ./compiler/nativeGen/GraphBase.hs -> ./compiler/utils/GraphBase.hs
     ./compiler/nativeGen/GraphColor.hs -> ./compiler/utils/GraphColor.hs
     ./compiler/nativeGen/GraphOps.hs -> ./compiler/utils/GraphOps.hs
     ./compiler/nativeGen/GraphPpr.hs -> ./compiler/utils/GraphPpr.hs