[3rdparty] Add php-ds polyfill

Signed-off-by: Roeland Jago Douma <roeland@famdouma.nl>

diff --git a/3rdparty b/3rdparty
index 5b2c4bd44fe8beddff3731516e53cc5ad9269c9b..a3fd9c27151df6b1d8920896a0eaf48dd303be94 160000 (submodule)
--- a/3rdparty
+++ b/3rdparty
@@ -1 +1 @@
-Subproject commit 5b2c4bd44fe8beddff3731516e53cc5ad9269c9b
+Subproject commit a3fd9c27151df6b1d8920896a0eaf48dd303be94