Fix build using base >= 4.6.0
Fix build using base >= 4.6.0

In base-4.6.0 (GHC 7.6.0), `catch` is no longer available in Prelude,
and System.Error.IO.catchIOError can be used instead.

This commit changes the Graphviz pretty-printing module accordingly.

sjfloat/accelerate,rrnewton/accelerate,robeverest/accelerate,robeverest/accelerate