fix three typos in comments

src/or/directory.c

@@ -349,7 +349,7 @@ should_use_directory_guards(const or_options_t *options)
   return 1;
 }
 
-/** Pick an unconsetrained directory server from among our guards, the latest
+/** Pick an unconstrained directory server from among our guards, the latest
  * networkstatus, or the fallback dirservers, for use in downloading
  * information of type <b>type</b>, and return its routerstatus. */
 static const routerstatus_t *

src/or/routerlist.c

@@ -1365,7 +1365,7 @@ router_pick_trusteddirserver(dirinfo_type_t type, int flags)
   return router_pick_dirserver_generic(trusted_dir_servers, type, flags);
 }
 
-/** Try to find a running fallback directory Flags are as for
+/** Try to find a running fallback directory. Flags are as for
  * router_pick_directory_server.
  */
 const routerstatus_t *
@@ -1374,7 +1374,7 @@ router_pick_fallback_dirserver(dirinfo_type_t type, int flags)
   return router_pick_dirserver_generic(fallback_dir_servers, type, flags);
 }
 
-/** Try to find a running fallback directory Flags are as for
+/** Try to find a running fallback directory. Flags are as for
  * router_pick_directory_server.
  */
 static const routerstatus_t *