malloc_hooks README.md: fix example compilation failures

Bug: N/A
Test: N/A
Change-Id: I017f47990417446f1bff5fc7a5bf7e53e8e1f85e
diff --git a/libc/malloc_hooks/README.md b/libc/malloc_hooks/README.md
index b418e1e..1747e8d 100644
--- a/libc/malloc_hooks/README.md
+++ b/libc/malloc_hooks/README.md
@@ -74,11 +74,11 @@
 ======================
 Below is a simple implementation intercepting only malloc/calloc calls.
 
-    void* new_malloc_hook(size_t bytes, const char* arg) {
+    void* new_malloc_hook(size_t bytes, const void* arg) {
       return orig_malloc_hook(bytes, arg);
     }
 
-    void orig_malloc_hook = __malloc_hook;
+    auto orig_malloc_hook = __malloc_hook;
     __malloc_hook = new_malloc_hook;
 
 Enabling Examples