Make fixes and improvements

- Introduce __assert_disable global
- Improve strsignal() thread safety
- Make system call tracing thread safe
- Fix SO_RCVTIMEO / SO_SNDTIMEO on Windows
- Refactor DescribeFoo() functions into one place
- Fix fork() on Windows when TLS and MAP_STACK exist
- Round upwards in setsockopt(SO_RCVTIMEO) on Windows
- Disable futexes on OpenBSD which seem extremely broken
- Implement a better kludge for monotonic time on Windows

libc/intrin/pthread_mutex_unlock.c

@@ -16,6 +16,7 @@
 │ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR             │
 │ PERFORMANCE OF THIS SOFTWARE.                                                │
 ╚─────────────────────────────────────────────────────────────────────────────*/
+#include "libc/assert.h"
 #include "libc/bits/atomic.h"
 #include "libc/calls/calls.h"
 #include "libc/errno.h"
@@ -33,19 +34,23 @@ int(pthread_mutex_unlock)(pthread_mutex_t *mutex) {
     case PTHREAD_MUTEX_ERRORCHECK:
       me = gettid();
       owner = atomic_load_explicit(&mutex->lock, memory_order_relaxed);
-      if (owner != me) return EPERM;
+      if (owner != me) {
+        assert(!"perm lock");
+        return EPERM;
+      }
       // fallthrough
     case PTHREAD_MUTEX_RECURSIVE:
       if (--mutex->reent) return 0;
       // fallthrough
     case PTHREAD_MUTEX_NORMAL:
       atomic_store_explicit(&mutex->lock, 0, memory_order_relaxed);
-      if ((IsLinux() || IsOpenbsd()) &&
+      if ((IsLinux() /* || IsOpenbsd() */) &&
           atomic_load_explicit(&mutex->waits, memory_order_relaxed) > 0) {
         _pthread_mutex_wake(mutex);
       }
       return 0;
     default:
+      assert(!"inva lock");
       return EINVAL;
   }
 }