ranap_common: Add function to wrap IEs into a RANAP_ProtocolIE_FieldPair_t

The FieldPair is a strange construct of RANAP Radio Access Bearer
assignment, where certain IEs appear in pairs.
diff --git a/src/ranap_common.h b/src/ranap_common.h
index 32a4436..599d912 100644
--- a/src/ranap_common.h
+++ b/src/ranap_common.h
@@ -616,3 +616,8 @@
 RANAP_IE_t *ranap_new_ie(RANAP_ProtocolIE_ID_t id, RANAP_Criticality_t criticality,
 			 asn_TYPE_descriptor_t *type, void *sptr);
 
+RANAP_ProtocolIE_FieldPair_t *ranap_new_ie_pair(RANAP_ProtocolIE_ID_t id,
+				RANAP_Criticality_t criticality1,
+				asn_TYPE_descriptor_t *type1, void *sptr1,
+				RANAP_Criticality_t criticality2,
+				asn_TYPE_descriptor_t *type2, void *sptr2);