hide "pre" to avoid clash with 

Hi Tristan,

when building this, I got this error:

~~~~~{.haskell}
src/LLVM/Analysis/CallGraphSCCTraversal.hs:155:20:
    Ambiguous occurrence `pre'
    It could refer to either `Control.Lens.pre',
                             imported from `Control.Lens' at src/LLVM/Analysis/CallGraphSCCTraversal.hs:23:1-19
                             (and originally defined in `Control.Lens.Fold')
                          or `Data.Graph.Interface.pre',
                             imported from `Data.Graph.Interface' at src/LLVM/Analysis/CallGraphSCCTraversal.hs:36:1-27
~~~~~

so I hid `Control.Lens.pre`