gsm_bts: add version and variant details

* add version string to gsm_bts
* add PCU version string to gsm_bts
* rename GSM_BTS_TYPE_OSMO_SYSMO -> GSM_BTS_OSMOBTS to avoid confusion
  between BTS model and variant
* add variant enum to gsm_bts_model using enum with variants for each
  hw vendor of OsmoBTS
* show connected PCU version (if available) in vty via 'show bts'

This will come in handy when logging details regarding particular BTS
reported via OML, see:

Related: OS#1614

Change-Id: I6710d53115f34634a7b70969cc05fd5c72ff8ab2
diff --git a/openbsc/src/libbsc/system_information.c b/openbsc/src/libbsc/system_information.c
index a2dd827..2610331 100644
--- a/openbsc/src/libbsc/system_information.c
+++ b/openbsc/src/libbsc/system_information.c
@@ -830,7 +830,7 @@
 	/* ip.access nanoBTS needs l2_plen!! */
 	switch (bts->type) {
 	case GSM_BTS_TYPE_NANOBTS:
-	case GSM_BTS_TYPE_OSMO_SYSMO:
+	case GSM_BTS_TYPE_OSMOBTS:
 		*output++ = GSM48_LEN2PLEN(l2_plen);
 		l2_plen++;
 		break;
@@ -865,7 +865,7 @@
 	/* ip.access nanoBTS needs l2_plen!! */
 	switch (bts->type) {
 	case GSM_BTS_TYPE_NANOBTS:
-	case GSM_BTS_TYPE_OSMO_SYSMO:
+	case GSM_BTS_TYPE_OSMOBTS:
 		*output++ = GSM48_LEN2PLEN(l2_plen);
 		l2_plen++;
 		break;
@@ -909,7 +909,7 @@
 	/* ip.access nanoBTS needs l2_plen!! */
 	switch (bts->type) {
 	case GSM_BTS_TYPE_NANOBTS:
-	case GSM_BTS_TYPE_OSMO_SYSMO:
+	case GSM_BTS_TYPE_OSMOBTS:
 		*output++ = GSM48_LEN2PLEN(l2_plen);
 		l2_plen++;
 		break;
@@ -946,7 +946,7 @@
 	/* ip.access nanoBTS needs l2_plen!! */
 	switch (bts->type) {
 	case GSM_BTS_TYPE_NANOBTS:
-	case GSM_BTS_TYPE_OSMO_SYSMO:
+	case GSM_BTS_TYPE_OSMOBTS:
 		*output++ = GSM48_LEN2PLEN(l2_plen);
 		l2_plen++;
 		break;