Add extended version tag and feature versions to output of -q.

src/saveload/extended_ver_sl.cpp

@@ -86,6 +86,20 @@ bool SlXvIsFeaturePresent(SlXvFeatureIndex feature, uint16 min_version, uint16 m
 	return _sl_xv_feature_versions[feature] >= min_version && _sl_xv_feature_versions[feature] <= max_version;
 }
 
+/**
+ * Returns true if @p feature is present and has a version inclusively bounded by @p min_version and @p max_version
+ */
+const char *SlXvGetFeatureName(SlXvFeatureIndex feature)
+{
+	const SlxiSubChunkInfo *info = _sl_xv_sub_chunk_infos;
+	for (; info->index != XSLFI_NULL; ++info) {
+		if (info->index == feature) {
+			return info->name;
+		}
+	}
+	return "(unknown feature)";
+}
+
 /**
  * Resets all extended feature versions to 0
  */