Hide dlmalloc symbols.

We need to leave dlmalloc_trim and dlmalloc_inspect_all exposed for
the VM, but if we're seriously looking at other malloc implementations,
that's something we're going to have to fix.

Bug: 11156955
Change-Id: If85156c280044f1616c09a3c50ba674aaf0e8d3a
diff --git a/libc/bionic/dlmalloc.c b/libc/bionic/dlmalloc.c
index 3a615d2..2d67392 100644
--- a/libc/bionic/dlmalloc.c
+++ b/libc/bionic/dlmalloc.c
@@ -46,14 +46,11 @@
   *((int**) 0xdeadbaad) = (int*) address;
 }
 
-static void* named_anonymous_mmap(size_t length)
-{
-    void* ret;
-    ret = mmap(NULL, length, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0);
-    if (ret == MAP_FAILED)
-        return ret;
-
-    __bionic_name_mem(ret, length, "libc_malloc");
-
-    return ret;
+static void* named_anonymous_mmap(size_t length) {
+  void* map = mmap(NULL, length, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0);
+  if (map == MAP_FAILED) {
+    return map;
+  }
+  __bionic_name_mem(map, length, "libc_malloc");
+  return map;
 }