Move SI-related defines

* move SI2quater related defines to shared header
* add define from OsmoBTS which checks for presence of a given SI
  message in gsm_bts struct. Rename it to avoid conflicts with OsmoBTS
  code and to match naming conventions of similar macros.

Change-Id: I11432c93c772d1ead6d45a7bb0f1d13d492c82f1
Related: OS#1660
diff --git a/openbsc/tests/gsm0408/gsm0408_test.c b/openbsc/tests/gsm0408/gsm0408_test.c
index 36f6993..5a78505 100644
--- a/openbsc/tests/gsm0408/gsm0408_test.c
+++ b/openbsc/tests/gsm0408/gsm0408_test.c
@@ -105,7 +105,7 @@
 	r = gsm_generate_si(bts, SYSINFO_TYPE_2quater);
 	if (r > 0)
 		printf("generated %s SI2quater [%02u/%02u]: [%d] %s\n",
-		       (bts->si_valid & (1 << SYSINFO_TYPE_2quater)) ? "valid" : "invalid",
+		       GSM_BTS_HAS_SI(bts, SYSINFO_TYPE_2quater) ? "valid" : "invalid",
 		       bts->si2q_index, bts->si2q_count, r,
 		       osmo_hexdump((void *)GSM_BTS_SI2Q(bts), GSM_MACBLOCK_LEN));
 	else