stats: Add osmo_ name prefix to identifiers

Since the the stat_item and stats functions and data types are meant
to be exported, they get an osmo_ prefix.

Sponsored-by: On-Waves ehf

[hfreyther: Prepended the enum values too. This was requested by
Jacob]
diff --git a/include/osmocom/gprs/gprs_ns.h b/include/osmocom/gprs/gprs_ns.h
index 42e0d88..7c3b23c 100644
--- a/include/osmocom/gprs/gprs_ns.h
+++ b/include/osmocom/gprs/gprs_ns.h
@@ -126,7 +126,7 @@
 	unsigned int nsvci_is_valid:1;
 
 	struct rate_ctr_group *ctrg;
-	struct stat_item_group *statg;
+	struct osmo_stat_item_group *statg;
 
 	/*! \brief which link-layer are we based on? */
 	enum gprs_ns_ll ll;