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

test/libc/runtime/fork_test.c

@@ -30,7 +30,9 @@
 #include "libc/sysv/consts/prot.h"
 #include "libc/sysv/consts/sig.h"
 #include "libc/testlib/ezbench.h"
+#include "libc/testlib/subprocess.h"
 #include "libc/testlib/testlib.h"
+#include "libc/thread/tls.h"
 
 TEST(fork, testPipes) {
   int a, b;
@@ -131,6 +133,14 @@ TEST(fork, childToChild) {
   sigprocmask(SIG_SETMASK, &oldmask, 0);
 }
 
+TEST(fork, preservesTlsMemory) {
+  int pid;
+  __get_tls()->tib_errno = 31337;
+  SPAWN(fork);
+  ASSERT_EQ(31337, __get_tls()->tib_errno);
+  EXITS(0);
+}
+
 void ForkInSerial(void) {
   int pid, ws;
   ASSERT_NE(-1, (pid = fork()));