Revert "Revert "Upgrade to dlmalloc 2.8.5.""

This reverts commit f72ee269274170cd46af2844a2fe88767fb6e43c.
diff --git a/libc/bionic/malloc_debug_common.c b/libc/bionic/malloc_debug_common.c
index 4105ab8..9333de9 100644
--- a/libc/bionic/malloc_debug_common.c
+++ b/libc/bionic/malloc_debug_common.c
@@ -195,9 +195,19 @@
     return dlmallinfo();
 }
 
-void* valloc(size_t bytes) {
-    /* assume page size of 4096 bytes */
-    return memalign( getpagesize(), bytes );
+size_t malloc_usable_size(void* mem)
+{
+    return dlmalloc_usable_size(mem);
+}
+
+void* valloc(size_t bytes)
+{
+    return dlvalloc(bytes);
+}
+
+void* pvalloc(size_t bytes)
+{
+    return dlpvalloc(bytes);
 }
 
 /* Support for malloc debugging.