Fix #77423: parse_url() will deliver a wrong host to user

Fix #77423: parse_url() will deliver a wrong host to user

To avoid that `parse_url()` returns an erroneous host, which would be
valid for `FILTER_VALIDATE_URL`, we make sure that only userinfo which
is valid according to RFC 3986 is treated as such.

For consistency with the existing url parsing code, we use ctype
functions, although that is not necessarily correct.