Deprecate gsm48_construct_ra()

It's just a tiny wrapper around gsm48_encode_ra() with less strict type
signature.

Related OS#1640
Change-Id: I79d6d1133afbf32e891a6b0e3a244c6885ea9614
diff --git a/include/osmocom/gsm/gsm48.h b/include/osmocom/gsm/gsm48.h
index 3ebca18..69431de 100644
--- a/include/osmocom/gsm/gsm48.h
+++ b/include/osmocom/gsm/gsm48.h
@@ -40,7 +40,7 @@
 /* Parse Routeing Area Identifier */
 void gsm48_parse_ra(struct gprs_ra_id *raid, const uint8_t *buf);
 void gsm48_encode_ra(struct gsm48_ra_id *out, const struct gprs_ra_id *raid);
-int gsm48_construct_ra(uint8_t *buf, const struct gprs_ra_id *raid);
+int gsm48_construct_ra(uint8_t *buf, const struct gprs_ra_id *raid) OSMO_DEPRECATED("Use gsm48_encode_ra() instead");
 
 int gsm48_number_of_paging_subchannels(struct gsm48_control_channel_descr *chan_desc);