[OML] parse attributes depending on BTS type

Some NM attributes are defined differently depending on
the BTS type.  Having one big nm_att_tlvdef[] table for
all BTS types is no longer sufficient.  This patch

* introduces 'struct gsm_bts_model' to describe a BTS model
* adds definitions of gsm_bts_model for BS-11 and nanoBTS
* changes the abis_nm_tlv_parse() function: include a bts pointer
diff --git a/openbsc/src/bsc_hack.c b/openbsc/src/bsc_hack.c
index 3122fae..581e9be 100644
--- a/openbsc/src/bsc_hack.c
+++ b/openbsc/src/bsc_hack.c
@@ -178,6 +178,9 @@
 	bsc_schedule_timer(&db_sync_timer, DB_SYNC_INTERVAL);
 }
 
+extern int bts_model_bs11_init(void);
+extern int bts_model_nanobts_init(void);
+
 int main(int argc, char **argv)
 {
 	int rc;
@@ -191,6 +194,9 @@
 	stderr_target = debug_target_create_stderr();
 	debug_add_target(stderr_target);
 
+	bts_model_bs11_init();
+	bts_model_nanobts_init();
+
 	/* enable filters */
 	debug_set_all_filter(stderr_target, 1);