Update the dlmalloc submodule

alexcrichton · alexcrichton · commit 49f7ccd35ff1 · 2018-02-10T07:01:27.000-08:00
A bug was recently fixed in dlmalloc which meant that released memory to the
system accidentally wasn't getting reused, causing programs to be far slower
than they should be!
diff --git a/src/dlmalloc b/src/dlmalloc
@@ -1 +1 @@
-Subproject commit a2b424b600235af58f453577c2da1b0e1de2ffa5
+Subproject commit 9b2dcac06c3e23235f8997b3c5f2325a6d3382df
