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/strace.internal.h

@@ -16,11 +16,11 @@
 COSMOPOLITAN_C_START_
 
 #ifdef SYSDEBUG
-#define STRACE(FMT, ...)                                  \
-  do {                                                    \
-    if (UNLIKELY(__strace > 0)) {                         \
-      __stracef(STRACE_PROLOGUE FMT "\n", ##__VA_ARGS__); \
-    }                                                     \
+#define STRACE(FMT, ...)                                   \
+  do {                                                     \
+    if (UNLIKELY(__strace > 0) && strace_enabled(0) > 0) { \
+      __stracef(STRACE_PROLOGUE FMT "\n", ##__VA_ARGS__);  \
+    }                                                      \
   } while (0)
 #else
 #define STRACE(FMT, ...) (void)0