Make signal handling work well across platforms

- Fix sigsuspend() on XNU
- Fix strsignal() on non-Linux
- Add unit tests for strsignal()
- Add unit tests for setitimer()
- Add unit tests for sigsuspend()
- Rewrite setitimer() for New Technology
- Rewrite nanosleep() for New Technology
- Polyfill SIGALRM on the New Technology
- select(0,0,0,0) on NT now calls pause()
- Remove some NTDLL calls that aren't needed
- Polyfill SA_NOCLDWAIT on the New Technology
- Polyfill SA_RESETHAND on the New Technology
- Polyfill sigprocmask() on the New Technology
- Polyfill SIGCHLD+SIG_IGN on the New Technology
- Polyfill SA_RESTART masking on the New Technology
- Deliver console signals from main thread on New Technology
- Document SA_RESTART behavior w/ @sarestartable / @norestart
- System call trace in MODE=dbg now prints inherited FDs and signal mask

libc/calls/kill-nt.c

@@ -16,6 +16,7 @@
 │ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR             │
 │ PERFORMANCE OF THIS SOFTWARE.                                                │
 ╚─────────────────────────────────────────────────────────────────────────────*/
+#include "libc/calls/calls.h"
 #include "libc/calls/getconsolectrlevent.h"
 #include "libc/calls/internal.h"
 #include "libc/dce.h"
@@ -35,7 +36,7 @@ textwindows int sys_kill_nt(int pid, int sig) {
   if (pid) {
     pid = ABS(pid);
     if ((event = GetConsoleCtrlEvent(sig)) != -1) {
-      /* kill(pid, SIGINT|SIGHUP|SIGQUIT) */
+      /* kill(pid, SIGINT|SIGQUIT) */
       if (__isfdkind(pid, kFdProcess)) {
         ntpid = GetProcessId(g_fds.p[pid].handle);
       } else if (!__isfdopen(pid)) {