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/log/checkfail.c

@@ -45,8 +45,8 @@ relegated void __check_fail(const char *suffix, const char *opstr,
   size_t i;
   va_list va;
   char hostname[32];
-  --__strace;
-  --__ftrace;
+  strace_enabled(-1);
+  ftrace_enabled(-1);
   e = errno;
   __start_fatal(file, line);
   __stpcpy(hostname, "unknown");