Improve locks and signals

- Introduce fast spinlock API
- Double rand64() perf w/ spinlock
- Improve raise() on New Technology
- Support gettid() across platforms
- Implement SA_NODEFER on New Technology
- Move the lock intrinsics into LIBC_INTRIN
- Make SIGTRAP recoverable on New Technology
- Block SIGCHLD in wait4() on New Technology
- Add threading prototypes for XNU and FreeBSD
- Rewrite abort() fixing its minor bugs on XNU/NT
- Shave down a lot of the content in libc/bits/bits.h
- Let signal handlers modify CPU registers on New Technology

third_party/python/Python/getcopyright.c

@@ -4,8 +4,8 @@
 │ Python 3                                                                     │
 │ https://docs.python.org/3/license.html                                       │
 ╚─────────────────────────────────────────────────────────────────────────────*/
-#include "libc/bits/bits.h"
 #include "libc/bits/weaken.h"
+#include "libc/intrin/cmpxchg.h"
 #include "libc/stdio/append.internal.h"
 #include "libc/str/str.h"
 #include "third_party/python/Include/pylifecycle.h"
@@ -30,7 +30,7 @@ Py_GetCopyright(void)
     const char *p;
     static bool once;
     static char *res;
-    if (cmpxchg(&once, 0, 1)) {
+    if (_cmpxchg(&once, 0, 1)) {
         appends(&res, "");
         for (p = *weaken(kLegalNotices); *p; p += strlen(p) + 1) {
             appends(&res, p);