Make received parameter in VIA header compatible with url encoded IPv6 address

[SoerenBusse]

This change will accept url encoded IPv6 addresses as the received parameter in the VIA header. Some sip server implementations tend to send the IPv6 address in url encoded (squared brackets) format altough this is not quite RFC compliat. However RFC5118 recommend to accept both IPv6 formats to make it compatible with all clients.

In this case we simply accept the ipv6reference as a valid via_address. We need to make sure to return the ipv6 address without brackets to via_received, otherwise we will get some odd behaviour where LinePhone will increate the count of squared brackets (like: [[2001:db8::1]]) after each REGISTRATION request (we're not removing the brackets). To prevent this we will use the return value of ipv6reference and pass it to via_received. To make it compatible with ipv4address and ipv6address we will return their value in via_address aswell.

Fixes issue: BelledonneCommunications/linphone-desktop#332

[jehandelalune]

thanks,
Under integration https://gitlab.linphone.org/BC/public/linphone-sdk/merge_requests/911

[jehandelalune]

Integrated in linphone-sdk by commit BelledonneCommunications/linphone-sdk@1108b7b