Expire lost items at the update instead of continuously

Replace thread DeleteItems running delete_lostitems() by simple
function delete_old_lostitems(), and call it from update_main().

src/lib/subs/lostsub.c

@@ -36,6 +36,8 @@
 
 #include "file.h"
 #include "lost.h"
+#include "misc.h"
+#include "optlist.h"
 
 static int findlost(short, natid, short, coord, coord, int);
 
@@ -118,3 +120,20 @@ findlost(short type, natid owner, short id, coord x, coord y, int free)
 
     return -1;
 }
+
+void
+delete_old_lostitems(void)
+{
+    time_t expiry_time = time(NULL) - hours(lost_keep_hours);
+    struct loststr lost;
+    int i;
+
+    for (i = 0; getlost(i, &lost); i++) {
+	if (!lost.lost_owner)
+	    continue;
+	if (lost.lost_timestamp >= expiry_time)
+	    continue;
+	lost.lost_owner = 0;
+	putlost(i, &lost);
+    }
+}

src/lib/update/main.c

@@ -173,6 +173,7 @@ update_main(void)
     unit_cargo_init();
     delete_old_announcements();
     delete_old_news();
+    delete_old_lostitems();
     /* Clear all the telegram flags */
     for (cn = 0; cn < MAXNOC; cn++)
 	clear_telegram_is_new(cn);