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/thread/xnu.internal.h

@@ -0,0 +1,25 @@
+#ifndef COSMOPOLITAN_LIBC_THREAD_XNU_INTERNAL_H_
+#define COSMOPOLITAN_LIBC_THREAD_XNU_INTERNAL_H_
+#if !(__ASSEMBLER__ + __LINKER__ + 0)
+COSMOPOLITAN_C_START_
+
+/**
+ * XNU thread system calls.
+ * @see darwin-libpthread/kern/kern_support.c
+ */
+
+void *bsdthread_create(void *func, void *func_arg, void *stack, void *pthread,
+                       uint32_t flags);
+int bsdthread_terminate(void *stackaddr, size_t freesize, uint32_t port,
+                        uint32_t sem);
+int bsdthread_register(void *threadstart, void *wqthread, uint32_t flags,
+                       void *stack_addr_hint, void *targetconc_ptr,
+                       uint32_t dispatchqueue_offset, uint32_t tsd_offset);
+int bsdthread_ctl(void *cmd, void *arg1, void *arg2, void *arg3);
+uint64_t thread_selfid(void);
+uint64_t thread_selfusage(void);
+int thread_selfcounts(int type, void *buf, uint64_t nbytes);
+
+COSMOPOLITAN_C_END_
+#endif /* !(__ASSEMBLER__ + __LINKER__ + 0) */
+#endif /* COSMOPOLITAN_LIBC_THREAD_XNU_INTERNAL_H_ */