QNetworkCookie::toRawForm(): Encode value string according to standard

QNetworkCookie::toRawForm() does not correctly encode the value string which is against RFC 2109 (As noted in the QNetworkCookie docs).

The RFC states that the value should not contain whitespace ("(informally, a sequence of non-special, non-white space characters)" Section 4.1).
It seems like a common approach is to URL-encode the value instead [1].

For this, QNetworkCookie::parseCookies()s helper method 'nextField()' would need to support percent encoded values too.

If this bug is rejected, the documentation should tell the user that one should manually encode values.

[1] stackoverflow.com/questions/572482/#tab-top