OpenSearch with GHC manual

[Sylvain Henry]

Hi,

Search engines often reference old versions of the GHC user guide. For 
instance with Google and the request "ghc unboxed tuples" I get the 
manual for 7.0.3, 5.04.1 and 6.8.2 as first results. With DuckDuckGo I 
get 6.12.3 and then "latest" versions of the manual.

So I have made a custom search engine for the latest manual (using 
OpenSearch spec). You can install it from the following page: 
http://haskus.fr/ghc/index.html like any other search engine.

Sphinx supports automatic generation of OpenSearch spec: 
http://www.sphinx-doc.org/en/1.4.8/config.html#confval-html_use_opensearch
Maybe we should use this to make the search engine easier to find and use.

As a side note, would it be possible to have a nicer URI for the latest 
doc? Currently it is: 
https://downloads.haskell.org/~ghc/latest/docs/html/users_guide/index.html
Something like https://haskell.org/ghc/doc/index.html would be better IMO.

Sylvain