Turn on -Wold-style-cast and fix the errors.

A couple of dodgy cases where we cast away const, but otherwise pretty boring.

Change-Id: Ibc39ebd525377792b5911464be842121c20f03b9
diff --git a/libc/bionic/tdestroy.cpp b/libc/bionic/tdestroy.cpp
index 49614b8..95c3e64 100644
--- a/libc/bionic/tdestroy.cpp
+++ b/libc/bionic/tdestroy.cpp
@@ -21,7 +21,7 @@
 // Destroy a tree and free all allocated resources.
 // This is a GNU extension, not available from BSD.
 void tdestroy(void* root, void (*destroy_func)(void*)) {
-  node_t* root_node = (node_t*) root;
+  node_t* root_node = reinterpret_cast<node_t*>(root);
   if (root_node == NULL) {
     return;
   }