gprs_bssgp: add utilities to send and parse BSSGP rim PDUs

At the moment libosmogb offers no convinient way to send RIM PDUs. Also
parsing an incoming RIM messages into destination, source routing
info and RIM container is not available.

Change-Id: I18134fd9938040d2facb6beee3732628b167ce8c
Related: SYS#5103
diff --git a/src/gb/libosmogb.map b/src/gb/libosmogb.map
index b012184..763ddc6 100644
--- a/src/gb/libosmogb.map
+++ b/src/gb/libosmogb.map
@@ -30,6 +30,7 @@
 bssgp_msgb_tlli_put;
 bssgp_msgb_ra_put;
 bssgp_parse_cell_id;
+bssgp_parse_rim_pdu;
 bssgp_parse_rim_ri;
 bssgp_set_bssgp_callback;
 bssgp_tx_bvc_block;
@@ -48,6 +49,7 @@
 bssgp_tx_resume;
 bssgp_tx_resume_ack;
 bssgp_tx_resume_nack;
+bssgp_tx_rim;
 bssgp_tx_simple_bvci;
 bssgp_tx_status;
 bssgp_tx_suspend;