Remove old 'deriving'.
Move deriving-310 to deriving.
Remove unused function.
Update boolean operators to non-deprecated versions.
Fix 'unused variable' warnings in PP.ml
Fix inexhaustive match in PP.ml.
Change 'open' to 'open!' to make shadowing explicit.
Remove unused 'open Notfound'
Merge branch 'fix-some-warnings' of https://github.com/yallop/links