sgsn: Create testcase that verifies that llmes get deleted

On an "unassignment" this code verifies that the LLME will vanish
from the list of LLMEs. We assume that this doesn't create a
memory leak.
diff --git a/openbsc/include/openbsc/gprs_llc.h b/openbsc/include/openbsc/gprs_llc.h
index 854b968..9689a37 100644
--- a/openbsc/include/openbsc/gprs_llc.h
+++ b/openbsc/include/openbsc/gprs_llc.h
@@ -240,4 +240,10 @@
 void gprs_llc_hdr_dump(struct gprs_llc_hdr_parsed *gph);
 int gprs_llc_fcs(uint8_t *data, unsigned int len);
 
+
+/* LLME handling routines */
+struct llist_head *gprs_llme_list(void);
+struct gprs_llc_lle *gprs_lle_get_or_create(const uint32_t tlli, uint8_t sapi);
+
+
 #endif