Make improvements

- We now serialize the file descriptor table when spawning / executing
  processes on Windows. This means you can now inherit more stuff than
  just standard i/o. It's needed by bash, which duplicates the console
  to file descriptor #255. We also now do a better job serializing the
  environment variables, so you're less likely to encounter E2BIG when
  using your bash shell. We also no longer coerce environ to uppercase

- execve() on Windows now remotely controls its parent process to make
  them spawn a replacement for itself. Then it'll be able to terminate
  immediately once the spawn succeeds, without having to linger around
  for the lifetime as a shell process for proxying the exit code. When
  process worker thread running in the parent sees the child die, it's
  given a handle to the new child, to replace it in the process table.

- execve() and posix_spawn() on Windows will now provide CreateProcess
  an explicit handle list. This allows us to remove handle locks which
  enables better fork/spawn concurrency, with seriously correct thread
  safety. Other codebases like Go use the same technique. On the other
  hand fork() still favors the conventional WIN32 inheritence approach
  which can be a little bit messy, but is *controlled* by guaranteeing
  perfectly clean slates at both the spawning and execution boundaries

- sigset_t is now 64 bits. Having it be 128 bits was a mistake because
  there's no reason to use that and it's only supported by FreeBSD. By
  using the system word size, signal mask manipulation on Windows goes
  very fast. Furthermore @asyncsignalsafe funcs have been rewritten on
  Windows to take advantage of signal masking, now that it's much more
  pleasant to use.

- All the overlapped i/o code on Windows has been rewritten for pretty
  good signal and cancelation safety. We're now able to ensure overlap
  data structures are cleaned up so long as you don't longjmp() out of
  out of a signal handler that interrupted an i/o operation. Latencies
  are also improved thanks to the removal of lots of "busy wait" code.
  Waits should be optimal for everything except poll(), which shall be
  the last and final demon we slay in the win32 i/o horror show.

- getrusage() on Windows is now able to report RUSAGE_CHILDREN as well
  as RUSAGE_SELF, thanks to aggregation in the process manager thread.

libc/calls/getrandom.c

@@ -23,6 +23,7 @@
 #include "libc/calls/internal.h"
 #include "libc/calls/struct/sigaction.h"
 #include "libc/calls/struct/sigset.h"
+#include "libc/calls/struct/sigset.internal.h"
 #include "libc/calls/syscall-sysv.internal.h"
 #include "libc/calls/syscall_support-nt.internal.h"
 #include "libc/calls/syscall_support-sysv.internal.h"
@@ -42,7 +43,6 @@
 #include "libc/nt/runtime.h"
 #include "libc/runtime/runtime.h"
 #include "libc/stdio/rand.h"
-#include "libc/stdio/xorshift.h"
 #include "libc/str/str.h"
 #include "libc/sysv/consts/at.h"
 #include "libc/sysv/consts/auxv.h"
@@ -181,18 +181,18 @@ ssize_t __getrandom(void *p, size_t n, unsigned f) {
     if (IsXnu() || IsOpenbsd()) {
       rc = GetRandomBsd(p, n, GetRandomEntropy);
     } else {
-      BEGIN_CANCELLATION_POINT;
+      BEGIN_CANCELATION_POINT;
       rc = sys_getrandom(p, n, f);
-      END_CANCELLATION_POINT;
+      END_CANCELATION_POINT;
     }
   } else if (IsFreebsd() || IsNetbsd()) {
     rc = GetRandomBsd(p, n, GetRandomArnd);
   } else if (IsMetal()) {
     rc = GetRandomMetal(p, n, f);
   } else {
-    BEGIN_CANCELLATION_POINT;
+    BEGIN_CANCELATION_POINT;
     rc = GetDevUrandom(p, n);
-    END_CANCELLATION_POINT;
+    END_CANCELATION_POINT;
   }
   return rc;
 }
@@ -222,7 +222,7 @@ ssize_t __getrandom(void *p, size_t n, unsigned f) {
  * On BSD OSes, this entire process is uninterruptible so be careful
  * when using large sizes if interruptibility is needed.
  *
- * Unlike getentropy() this function is a cancellation point. But it
+ * Unlike getentropy() this function is a cancelation point. But it
  * shouldn't be a problem, unless you're using masked mode, in which
  * case extra care must be taken to consider the result.
  *
@@ -243,7 +243,7 @@ ssize_t __getrandom(void *p, size_t n, unsigned f) {
  * @raise ECANCELED if thread was cancelled in masked mode
  * @raise EFAULT if the `n` bytes at `p` aren't valid memory
  * @raise EINTR if we needed to block and a signal was delivered instead
- * @cancellationpoint
+ * @cancelationpoint
  * @asyncsignalsafe
  * @restartable
  * @vforksafe
@@ -264,13 +264,13 @@ ssize_t getrandom(void *p, size_t n, unsigned f) {
 __attribute__((__constructor__)) static textstartup void getrandom_init(void) {
   int e, rc;
   if (IsWindows() || IsMetal()) return;
-  BLOCK_CANCELLATIONS;
+  BLOCK_CANCELATION;
   e = errno;
   if (!(rc = sys_getrandom(0, 0, 0))) {
     have_getrandom = true;
   } else {
     errno = e;
   }
-  ALLOW_CANCELLATIONS;
+  ALLOW_CANCELATION;
   STRACE("sys_getrandom(0,0,0) → %d% m", rc);
 }