eap-aka-3gpp: Add plugin that implements 3GPP MILENAGE algorithm in software

This is similar to the eap-aka-3gpp2 plugin. K (optionally concatenated
with OPc) may be configured as binary EAP secret in ipsec.secrets or
swanctl.conf.

Based on a patch by Thomas Strangert.

Fixes #2326.

conf/plugins/eap-aka-3ggp2.opt

@@ -1 +0,0 @@
-charon.plugins.eap-aka-3ggp2.seq_check =

conf/plugins/eap-aka-3gpp.opt

@@ -0,0 +1,3 @@
+charon.plugins.eap-aka-3gpp.seq_check =
+	Enable to activate sequence check of the AKA SQN values	in order to trigger
+	resync cycles.

conf/plugins/eap-aka-3gpp2.opt

@@ -0,0 +1,4 @@
+charon.plugins.eap-aka-3gpp2.seq_check =
+	Enable to activate sequence check of the AKA SQN values in order to trigger
+	resync cycles.
+