gsm0808: Add AoIP specific elements to gsm0808_create_... functions

the classic A implementation in libosmocore lacks support for AoIP
message elements. This patch adds support for AoIP by adding a set
of new gsm0808_create_..., which support the missing AoIP message
elements

Change-Id: I77f866abec1822d19871052f3c647ad782785b34
diff --git a/tests/gsm0808/gsm0808_test.ok b/tests/gsm0808/gsm0808_test.ok
index eb43126..f406551 100644
--- a/tests/gsm0808/gsm0808_test.ok
+++ b/tests/gsm0808/gsm0808_test.ok
@@ -1,5 +1,6 @@
 Testing generation of GSM0808 messages
 Testing creating Layer3
+Testing creating Layer3 (AoIP)
 Testing creating Reset
 Testing creating Clear Command
 Testing creating Clear Complete
@@ -8,7 +9,9 @@
 Testing creating CM U
 Testing creating SAPI Reject
 Testing creating Assignment Complete
+Testing creating Assignment Complete (AoIP)
 Testing creating Assignment Failure
+Testing creating Assignment Failure (AoIP)
 Testing creating Clear Request
 Testing creating DTAP
 Testing prepend DTAP