MEDIUM: http: block non-ASCII characters in URIs by default

MEDIUM: http: block non-ASCII characters in URIs by default

These ones are invalid and blocked unless "option accept-invalid-http-request"
is specified in the frontend. In any case, the faulty request is logged.

Note that some of the remaining invalid chars are still not checked against,
those are the invalid ones between 32 and 127 :

    34 ('"'), 60 ('<'), 62 ('>'), 92 ('\'), 94 ('^'),
    96 ('`'), 123 ('{'), 124 ('|'), 125 ('}')

Using a lookup table might be better at some point.