Update Haddock to new pattern synonym type signature syntax
Follow changes from #9812
Changes to reflect refactoring in GHC as part of #7484
Follow API changes in D426

Signed-off-by: Austin Seipp <aseipp@pobox.com>
Support for PartialTypeSignatures
For pattern synonyms, render "pattern" as a keyword
hide projectVersion from DynFlags since it clashes with Haddock.Version.projectVersion