Rollup merge of rust-lang#48085 - alexcrichton:update-dlmalloc, r=Mark-Simulacrum

kennytm · kennytm · commit c888f723042c · 2018-02-11T00:51:56.000+08:00
Update the dlmalloc submodule

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
