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/sig.internal.h

@@ -1,16 +1,20 @@
 #ifndef COSMOPOLITAN_LIBC_CALLS_SIGNALS_INTERNAL_H_
 #define COSMOPOLITAN_LIBC_CALLS_SIGNALS_INTERNAL_H_
 #include "libc/calls/struct/sigset.h"
+#include "libc/calls/ucontext.h"
 
 #define __SIG_QUEUE_LENGTH        8
 #define __SIG_POLLING_INTERVAL_MS 50
+#define __SIG_LOGGING_INTERVAL_MS 1700
 
 #if !(__ASSEMBLER__ + __LINKER__ + 0)
 COSMOPOLITAN_C_START_
 
 bool __sig_check(bool) hidden;
+bool __sig_handle(bool, int, int, ucontext_t *) hidden;
 int __sig_add(int, int) hidden;
-sigset_t __sig_mask(const sigset_t *) hidden;
+int __sig_mask(int, const sigset_t *, sigset_t *) hidden;
+int __sig_raise(int, int) hidden;
 
 COSMOPOLITAN_C_END_
 #endif /* !(__ASSEMBLER__ + __LINKER__ + 0) */