Fix for uncontrolled growth of slot list under certain patterns

of connection/disconnection without invocation.  Refs #4089.



[SVN r61243]

libs/signals2

@@ -1 +1 @@
-Subproject commit c2d62855537ce9fd66ca2c2cb35faaadbbe7515f
+Subproject commit 62dce534c85283337420334b0cb311866529542f