if the cookie is a session cookie indicate it

previously session cookies were simply displayed as having an expiry
in 1970 which was unhelpful.

content/urldb.c

@@ -112,6 +112,12 @@
 #include "content/content.h"
 #include "content/urldb.h"
 
+/**
+ * cookie entry.
+ *
+ * \warn This *must* be kept in sync with the public interface in
+ *   netsurf/cookie_db.h
+ */
 struct cookie_internal_data {
 	struct cookie_internal_data *prev;	/**< Previous in list */
 	struct cookie_internal_data *next;	/**< Next in list */

desktop/cookie_manager.c

@@ -294,8 +294,14 @@ cookie_manager_set_treeview_field_data(struct cookie_manager_entry *e,
 			&e->data[COOKIE_M_PATH], strdup(data->path));
 
 	/* Set the Expires date field */
+	if (data->expires == -1) {
+		cookie_manager_field_builder(COOKIE_M_EXPIRES,
+			&e->data[COOKIE_M_EXPIRES],
+			strdup(messages_get("CookieManagerSession")));
+	} else {
 		cookie_manager_field_builder_time(COOKIE_M_EXPIRES,
 			&e->data[COOKIE_M_EXPIRES], &data->expires);
+	}
 
 	/* Set the Last used date field */
 	cookie_manager_field_builder_time(COOKIE_M_LAST_USED,

resources/FatMessages

@@ -1273,6 +1273,7 @@ nl.all.TreeviewLabelFolder:Map:
 
 # Cookie Manager field values
 #
+en.all.CookieManagerSession:Session
 en.all.CookieManagerHTTPS:Secure hosts via https only
 de.all.CookieManagerHTTPS:Secure hosts via https only
 fr.all.CookieManagerHTTPS:Hôtes sécurisés via https uniquement