gb: Make suspend_ref a plain uint8_t instead of a uint8_t*

The OpenSUSE build is not happy about the uint8_t to uint8_t*
assignment. As the suspend_ref is a mandatory field we can make
it a plain uint8_t. Increase the LIBVERSION as the ABI has changed.
diff --git a/include/osmocom/gprs/gprs_bssgp.h b/include/osmocom/gprs/gprs_bssgp.h
index 949dbdc..8ca42bf 100644
--- a/include/osmocom/gprs/gprs_bssgp.h
+++ b/include/osmocom/gprs/gprs_bssgp.h
@@ -47,7 +47,7 @@
 	/* specific fields */
 	union {
 		struct {
-			uint8_t *suspend_ref;
+			uint8_t suspend_ref;
 		} resume;
 	} u;
 };