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/usleep.c

@@ -16,18 +16,18 @@
 │ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR             │
 │ PERFORMANCE OF THIS SOFTWARE.                                                │
 ╚─────────────────────────────────────────────────────────────────────────────*/
+#include "libc/calls/internal.h"
 #include "libc/calls/strace.internal.h"
 #include "libc/calls/struct/timespec.h"
+#include "libc/sysv/errfuns.h"
 #include "libc/time/time.h"
 
 /**
  * Sleeps for particular amount of microseconds.
+ * @norestart
  */
 int usleep(uint32_t microseconds) {
-  int rc;
-  rc = nanosleep(&(struct timespec){(uint64_t)microseconds / 1000000,
-                                    (uint64_t)microseconds % 1000000 * 1000},
-                 NULL);
-  STRACE("usleep(%'u) → %d% m", microseconds, rc);
-  return rc;
+  return nanosleep(&(struct timespec){(uint64_t)microseconds / 1000000,
+                                      (uint64_t)microseconds % 1000000 * 1000},
+                   NULL);
 }