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/pthread_create.cpp b/libc/bionic/pthread_create.cpp
index e4abee9..7406b35 100644
--- a/libc/bionic/pthread_create.cpp
+++ b/libc/bionic/pthread_create.cpp
@@ -62,7 +62,7 @@
   thread->tls[TLS_SLOT_SELF] = thread->tls;
   thread->tls[TLS_SLOT_THREAD_ID] = thread;
   // GCC looks in the TLS for the stack guard on x86, so copy it there from our global.
-  thread->tls[TLS_SLOT_STACK_GUARD] = (void*) __stack_chk_guard;
+  thread->tls[TLS_SLOT_STACK_GUARD] = reinterpret_cast<void*>(__stack_chk_guard);
 }
 
 void __init_alternate_signal_stack(pthread_internal_t* thread) {