Implement OverloadedRecordFields extension

html-test/ref/OverloadedRecordFields.html

html-test/src/OverloadedRecordFields.hs

src/Haddock/Backends/Hoogle.hs

src/Haddock/Backends/LaTeX.hs

src/Haddock/Backends/Xhtml.hs

src/Haddock/Backends/Xhtml/Decl.hs

src/Haddock/Backends/Xhtml/Names.hs

src/Haddock/Convert.hs

src/Haddock/Interface/Create.hs

src/Haddock/Interface/LexParseRn.hs

src/Haddock/Interface/Rename.hs

src/Haddock/InterfaceFile.hs

src/Haddock/Types.hs

src/Haddock/Utils.hs