Add support for IPv4v6 End User Addresses

Before this commit, when an MS requested an ipv4v6 context osmo-ggsn
returned an error stating the type was unknown, and this text was
printed in the log:
Processing create PDP context request for APN 'ims'
Cannot decode EUA from MS/SGSN: f1 8d

This patch has been tested with an MS running the 3 types of addresses:
- IPv4 and IPv6: no regressions observed, the context is activated and
packets are sent to the ggsn.
- IPv4v6: Wireshark correctly parses request and reponse, and then
ICMPv6 traffic from both sides. Finally I see the MS using the IPv4 and
IPv6 DNS addresses advertised and TCP traffic over IPv4 (because
probably my IPv6 network setup is not correct). I also checked I can
disable/enable data (pdp ctx delete and activate) several times without
any issue.

Change-Id: Ic820759167fd3bdf329cb11d4b942e903fe50af5
diff --git a/tests/lib/in46a_v6_test.ok b/tests/lib/in46a_v6_test.ok
index d092591..10dc7f4 100644
--- a/tests/lib/in46a_v6_test.ok
+++ b/tests/lib/in46a_v6_test.ok
@@ -3,6 +3,8 @@
 Testing in46a_ntop() with IPv6 addresses
 res = 102:304:506:708:90a:b0c:d0e:f10
 Testing in46a_equal() with IPv6 addresses
-testing in46a_to_eua() with IPv6 addresses
+Testing in46a_to_eua() with IPv6 addresses
 Testing in46a_from_eua() with IPv6 addresses
+Testing in46a_to_eua() with IPv4v6 addresses
+Testing in46a_from_eua() with IPv4v6 addresses
 Testing in46a_netmasklen() with IPv6 addresses