Missing exportations in the Text.PrettyPrint module

The [documentation](http://hackage.haskell.org/package/pretty-1.1.3.3/docs/Text-PrettyPrint.html) for `Text.PrettyPrint` says:

> This module should be used as opposed to the HughesPJ module. Both are equivalent though as this module simply re-exports the other.

However, for example the function `maybeParens` defined in `Text.PrettyPrint.HughesPJ` is not exported by `Text.PrettyPrint`:

```
import Text.PrettyPrint

foo :: Bool -> Doc -> Doc
foo = maybeParens

-- Test.hs:5:7: error:
-- Variable not in scope: maybeParens :: Bool -> Doc -> Doc
```

Note also that in the above documentation, the module name 'HughesPJ' should be 'Text.PrettyPrint.HughesPJ'.

pretty version: 1.1.3.3.