receiveHTTP does not preprocess the incoming URI before it is parsed

Because of the strict parsing of URIs by Network.URI.parseURIReference, parseRequestHead fails on this "almost valid" URI:

```
ghci> parseRequestHead ["GET http://fonts.googleapis.com/css?family=Roboto:300|Open+Sans:700|Open+Sans:300&lang=en HTTP/1.1"]
ghci> Left (ErrorParse "parseRequestHead Request command line parse failure: GET http://fonts.googleapis.com/css?family=Roboto:300|Open+Sans:700|Open+Sans:300&lang=en HTTP/1.1")
```

Replacing the pipe characters with %7C allows the URI to parse.

receiveHTTP, or maybe parseRequestHead, should probably try to escape the characters that are considered invalid for URIs, before sending the string through parseURIReference.

In that regard, `escapeURIString isAllowedInURI` from Network.URI may be handy.

(Something about "be conservative in what you send, be liberal in what you accept" prompted me to raise this issue.)

Start by reading receiveHTTP and parseRequestHead, then inspect how the incoming request URI reaches Network.URI.parseURIReference. Check the suggested escapeURIString isAllowedInURI behavior for invalid URI characters, and consider both entry points named in the issue. Done means the shown URI is accepted while already valid URIs continue to parse correctly.

Escrito por el modelo de indexación a partir del texto del issue.