gsup: Introduce OSMO_GSUP_NUM_VECTORS_REQ_IE

This is a bit of a hack, as we want to maintain binary compatibility
without breaking existing users of libosmocore.  To do so, we use the
'num_auth_vectors' field in two ways now:

* In the existing use case as part of SEND_AUTH_INFO_RESPONSE, it
  indicates the number of vectors stored in the 'auth_vectors' field

* In the new use case as part of SEND_AUTH_INFO_REQUEST, it indicates
  the number of vectors actually requested by the MSC/SGSN/MME.

Change-Id: Iaecc47280f8ce54f3e3a888c1cfc160735483d0f
diff --git a/tests/gsup/gsup_test.ok b/tests/gsup/gsup_test.ok
index db8bc2f..ef2aec6 100644
--- a/tests/gsup/gsup_test.ok
+++ b/tests/gsup/gsup_test.ok
@@ -77,4 +77,6 @@
           E Abort OK
   Testing E Routing Error
           E Routing Error OK
+  Testing Send Authentication Info Request (10 Vectors)
+          Send Authentication Info Request (10 Vectors) OK
 Done.