Forward ETWS Primary Notification to MS

Receive an Application Information Request from the BTS via PCU
interface. Construct a Packet Application Information message from it
(3GPP TS 44.060 11.2.47) and send it to all MS with active TBF.

The TTCN-3 test infrastructure to test this feature is not quite ready
yet, so I've added C unit tests instead.

Related: OS#4048
Change-Id: Ie35959f833f46bde5f2126314b6f96763f863b36
diff --git a/src/gprs_rlcmac.h b/src/gprs_rlcmac.h
index 7a3a7af..16cb05f 100644
--- a/src/gprs_rlcmac.h
+++ b/src/gprs_rlcmac.h
@@ -31,6 +31,7 @@
 #include <osmocom/core/linuxlist.h>
 #include <osmocom/core/timer.h>
 #include <osmocom/core/bitvec.h>
+#include <osmocom/pcu/pcuif_proto.h>
 }
 #endif
 
@@ -94,6 +95,8 @@
 int gprs_rlcmac_paging_request(uint8_t *ptmsi, uint16_t ptmsi_len,
 	const char *imsi);
 
+struct msgb *gprs_rlcmac_app_info_msg(const struct gsm_pcu_if_app_info_req *req);
+
 int gprs_rlcmac_rcv_rts_block(struct gprs_rlcmac_bts *bts,
 	uint8_t trx, uint8_t ts,
         uint32_t fn, uint8_t block_nr);