gsm0808: Add create functions for BSS_MAP_MSG_PAGING

gsm0808.h/c lacks functionality to generate BSS_MAP_MSG_PAGING messages. These
messages are required if the code is used in an MSC implementation.

This commit adds a gsm0808_create_paging() function, that generates an A/AoiP
BSS_MAP_MSG_PAGING message.

Change-Id: I9afecf0109305ca5153bf081bb29cd94071dd2b7
diff --git a/include/osmocom/gsm/gsm0808.h b/include/osmocom/gsm/gsm0808.h
index 9738a55..990fd74 100644
--- a/include/osmocom/gsm/gsm0808.h
+++ b/include/osmocom/gsm/gsm0808.h
@@ -57,6 +57,9 @@
 				     *scl);
 struct msgb *gsm0808_create_assignment_failure(uint8_t cause, uint8_t *rr_cause);
 struct msgb *gsm0808_create_clear_rqst(uint8_t cause);
+struct msgb *gsm0808_create_paging(const char *imsi, const uint32_t *tmsi,
+				   const struct gsm0808_cell_id_list *cil,
+				   const uint8_t *chan_needed);
 
 struct msgb *gsm0808_create_dtap(struct msgb *msg, uint8_t link_id);
 void gsm0808_prepend_dtap_header(struct msgb *msg, uint8_t link_id);