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/calls/kill.c

@@ -18,7 +18,9 @@
 ╚─────────────────────────────────────────────────────────────────────────────*/
 #include "libc/calls/calls.h"
 #include "libc/calls/internal.h"
+#include "libc/calls/strace.internal.h"
 #include "libc/dce.h"
+#include "libc/str/str.h"
 
 /**
  * Sends signal to process.
@@ -38,9 +40,12 @@
  * @asyncsignalsafe
  */
 int kill(int pid, int sig) {
+  int rc;
   if (!IsWindows()) {
-    return sys_kill(pid, sig, 1);
+    rc = sys_kill(pid, sig, 1);
   } else {
-    return sys_kill_nt(pid, sig);
+    rc = sys_kill_nt(pid, sig);
   }
+  STRACE("kill(%d, %s) → %d% m", pid, strsignal(sig), rc);
+  return rc;
 }