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/intrin/pthread_atfork.c

@@ -74,6 +74,7 @@
  * @param parent is run by fork() after forking happens in parent process
  * @param child is run by fork() after forking happens in childe process
  * @return 0 on success, or errno on error
+ * @raise ENOMEM if we require more vespene gas
  */
 int pthread_atfork(atfork_f prepare, atfork_f parent, atfork_f child) {
   if (_weaken(_pthread_atfork)) {