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/calls/prctl.c

@@ -19,22 +19,10 @@
 #include "libc/calls/calls.h"
 #include "libc/calls/strace.internal.h"
 #include "libc/errno.h"
+#include "libc/intrin/describeflags.internal.h"
 #include "libc/sysv/consts/pr.h"
 #include "libc/sysv/errfuns.h"
 
-static const char *DescribePrctlOperation(int x) {
-  switch (x) {
-    case PR_SET_NO_NEW_PRIVS:
-      return "PR_SET_NO_NEW_PRIVS";
-    case PR_SET_SECCOMP:
-      return "PR_SET_SECCOMP";
-    case PR_GET_SECCOMP:
-      return "PR_GET_SECCOMP";
-    default:
-      return "PRCTL_???";
-  }
-}
-
 /**
  * Tunes process on Linux.
  *