Re-add dlmalloc for 32 bit.

It turns out that appportable has a version that calls dlmalloc directly.
Re-add the dlmalloc symbol for 32 bit only as a compatibility shim that
calls malloc.

Bug: 17881362

(cherry pick commit from c9734d24d92f4737f5ab3808c77d816a1b084582)

Change-Id: Iee9a777f66a1edb407d7563a60792b767ac4f83a
Merge "Re-add dlmalloc for 32 bit."