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

libc/log/leaks.c

@@ -20,6 +20,7 @@
 #include "libc/calls/strace.internal.h"
 #include "libc/intrin/asan.internal.h"
 #include "libc/intrin/kprintf.h"
+#include "libc/intrin/lockcmpxchg.h"
 #include "libc/runtime/internal.h"
 #include "libc/runtime/memtrack.internal.h"
 #include "libc/runtime/runtime.h"
@@ -72,7 +73,7 @@ static noasan bool HasLeaks(void) {
  */
 noasan void CheckForMemoryLeaks(void) {
   struct mallinfo mi;
-  if (!lockcmpxchg(&once, false, true)) {
+  if (!_lockcmpxchg(&once, false, true)) {
     kprintf("CheckForMemoryLeaks() may only be called once\n");
     exit(1);
   }