bts_feature: Introduce feature to speak to PCU

This feature provides the BSC with information on whether the BTS talks
the IPAC_PROTO_EXT_PCU osmocom extension over the underlying IPA
multiplex of the OML link.

Related: SYS#5303
Change-Id: Id62421f7f5540875ac877a187757f2cf0556bd02
diff --git a/include/osmocom/gsm/bts_features.h b/include/osmocom/gsm/bts_features.h
index 93d35f3..8bd5ef5 100644
--- a/include/osmocom/gsm/bts_features.h
+++ b/include/osmocom/gsm/bts_features.h
@@ -29,6 +29,7 @@
 	BTS_FEAT_ACCH_REP,
 	BTS_FEAT_CCN, /* Is CCN supported by the cell? TS 44.060 sec 8.8.2 */
 	BTS_FEAT_VAMOS, /* Is the BTS VAMOS capable? */
+	BTS_FEAT_ABIS_OSMO_PCU, /* BTS supports forwarding data to PCUIF over IPA OML multiplex */
 	_NUM_BTS_FEAT
 };