libnm: belatedly expose nm_ethtool_optname_is_feature() in libnm

Also, plan right away to backport this symbol all the way back to
1.14.8. As such, we only need to add it once, with the right linker
version "libnm_1_14_8".

But still, the symbols first appears on a major release 1.20.0.

(cherry picked from commit a4c1489507)

libnm-core/nm-setting-ethtool.c

@@ -40,13 +40,17 @@
 
 /**
  * nm_ethtool_optname_is_feature:
- * @optname: the option name to check
+ * @optname: (allow-none): the option name to check
  *
  * Checks whether @optname is a valid option name for an offload feature.
  *
  * %Returns: %TRUE, if @optname is valid
  *
- * Since: 1.14
+ * Since: 1.18.2
+ *
+ * Note that nm_ethtool_optname_is_feature() was first added to the libnm header files
+ * in 1.14.0 but forgot to actually add to the library. This happened belatedly in 1.20.0 and
+ * the stable versions 1.18.2, 1.16.4 and 1.14.8 (with linker version "libnm_1_14_8").
  */
 gboolean
 nm_ethtool_optname_is_feature (const char *optname)

libnm-core/nm-setting-ethtool.h

@@ -84,7 +84,7 @@ G_BEGIN_DECLS
 #define NM_ETHTOOL_OPTNAME_FEATURE_TX_UDP_TNL_SEGMENTATION      "feature-tx-udp_tnl-segmentation"
 #define NM_ETHTOOL_OPTNAME_FEATURE_TX_VLAN_STAG_HW_INSERT       "feature-tx-vlan-stag-hw-insert"
 
-NM_AVAILABLE_IN_1_14
+NM_AVAILABLE_IN_1_18_2
 gboolean nm_ethtool_optname_is_feature (const char *optname);
 
 /*****************************************************************************/

libnm/libnm.ver

@@ -1445,6 +1445,10 @@ global:
 	nm_utils_sriov_vf_to_str;
 } libnm_1_12_0;
 
+libnm_1_14_8 {
+	nm_ethtool_optname_is_feature;
+} libnm_1_14_0;
+
 libnm_1_16_0 {
 global:
 	nm_client_add_and_activate_connection2;