Optimized cleanup of slot list when a signal is invoked with a large number

of disconnected slots still in the slot list.


[SVN r55143]

libs/signals2

@@ -1 +1 @@
-Subproject commit e6727f317cf36be8fd0e4f526b16a8c64b188db6
+Subproject commit c604fa61c7ce866804d6c133461ea6930bd57b30