UnicodeSyntax

GHC has [an extension called UnicodeSyntax](http://www.haskell.org/ghc/docs/7.2.1/html/users_guide/syntax-extns.html) that lets you use unicode symbols for various keywords in the Haskell syntax. It would be nice if I could automatically UnicodeSyntaxify code. This would involve adding the extension at the top of the module if not already there, and replacing all replaceable symbols with their unicode counterparts.

Read the linked GHC UnicodeSyntax documentation first to enumerate the supported keyword and symbol replacements. Then locate stylish-haskell’s formatting entry points and determine how to add the extension only when needed; done means Haskell code is consistently converted to UnicodeSyntax form without changing unrelated syntax.

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