IDN support in streams

As discussed in this thread: http://marc.info/?l=php-internals&m=141107203812897, this PR add IDN support in streams. The way it is down (by adding a new internal field in the `php_url` struct) will allow adding easily IDN validation in `ext/filter`.

Tests must be enhanced, it would be great if the PHP org can setup for test purpose:
- An HTTP, HTTPS and FTP enabled server with an IDN