gsm0808: Implement helper functions for CONFUSION BSSMAP message decoding.

Also add a test for an actual CONFUSION message parsing.

Change-Id: If8afd2d096fb66c6c2f255a08fc1129de3d09cec
diff --git a/src/gsm/libosmogsm.map b/src/gsm/libosmogsm.map
index ce55746..70b3916 100644
--- a/src/gsm/libosmogsm.map
+++ b/src/gsm/libosmogsm.map
@@ -159,6 +159,8 @@
 gsm0808_cause_name;
 gsm0808_cause_class_name;
 gsm0808_get_cause;
+gsm0808_diagnostics_octet_location_str;
+gsm0808_diagnostics_bit_location_str;
 gsm0808_create_ass;
 gsm0808_create_ass2;
 gsm0808_create_assignment_completed;