Merge updated Pool lib from trunk.

Fixes #1252.
Fixes #2696.
Fixes #4960.
Fixes #5526.
Fixes #5568.
Fixes #5700.

[SVN r73495]

libs/pool

@@ -1 +1 @@
-Subproject commit 646b32b5e91598dfae59ea40b7a81318dedac3ae
+Subproject commit 3b4171e1a053350702449a9a24a99b31842971dc