Non-ASCII mailbox names characters must be utf7 encoded
Non-ASCII mailbox names characters must be utf7 encoded

I've added some code to encode mailbox names, when they contain non-ASCII characters.

> Mailbox names that contain international characters besides those in the printable ASCII space have to be encoded with imap_utf7_encode().
Reference: https://www.php.net/manual/en/function.imap-open.php (see **Parameter: mailbox**)

Original strings:
```
"{imap.example.com:993/imap/ssl}Hilfä & Süpport™"
"{imap.example.com:993/imap/ssl}Hilfe_Support"
```

Updated strings with the above code change:
```
"{imap.example.com:993/imap/ssl}Hilf&w6Q- &- S&w7w-pport&4oSi-"
"{imap.example.com:993/imap/ssl}Hilfe_Support"
```
barbushin/php-imap