Added shared_connection_block::connection() query, and a

connection::operator!=().  Added a test of shared_connection_block
assignment.


[SVN r53131]

libs/signals2

@@ -1 +1 @@
-Subproject commit d43635d4be6adae0237231e63b7dd3a19a4fc439
+Subproject commit 6183fc34c3212d4ea34b7076a810c5377b6e470b