Make more threading improvements

- ASAN memory morgue is now lockless
- Make C11 atomics header more portable
- Rewrote pthread keys support to be lockless
- Simplify Python's unicode table unpacking code
- Make crash report write(2) closer to being atomic
- Make it possible to strace/ftrace a single thread
- ASAN now checks nul-terminated strings fast and properly
- Windows fork() now restores TLS memory of calling thread

libc/thread/pthread_zombies.c

@@ -78,6 +78,6 @@ void _pthread_zombies_purge(void) {
   }
 }
 
-__attribute__((__constructor__)) static void init(void) {
+__attribute__((__constructor__)) static void _pthread_zombies_init(void) {
   atexit(_pthread_zombies_harvest);
 }