Rewrite special file handling on Windows

This change gets GNU grep working. What caused it to not work, is it
wouldn't write to an output file descriptor when its dev/ino equaled
/dev/null's. So now we invent special dev/ino values for these files

libc/proc/cocmd.c

@@ -96,11 +96,19 @@ static wontreturn void UnsupportedSyntax(unsigned char c) {
 }
 
 static void Open(const char *path, int fd, int flags) {
-  close(fd);
-  if (open(path, flags, 0644) == -1) {
+  int tmpfd;
+  // use open+dup2 to support things like >/dev/stdout
+  if ((tmpfd = open(path, flags, 0644)) == -1) {
     perror(path);
     _Exit(1);
   }
+  if (tmpfd != fd) {
+    if (dup2(tmpfd, fd) == -1) {
+      perror("dup2");
+      _Exit(1);
+    }
+    close(tmpfd);
+  }
 }
 
 static int SystemExec(void) {

libc/proc/fork-nt.c

@@ -67,10 +67,8 @@
 #include "libc/thread/itimer.internal.h"
 #include "libc/thread/posixthread.internal.h"
 #include "libc/thread/tls.h"
-
 #ifdef __x86_64__
 
-extern int64_t __wincrashearly;
 void __keystroke_wipe(void);
 
 static textwindows wontreturn void AbortFork(const char *func) {
@@ -399,7 +397,7 @@ textwindows int sys_fork_nt(uint32_t dwCreationFlags) {
     __tls_enabled_set(true);
     // clear pending signals
     tib->tib_sigpending = 0;
-    __sig.pending = 0;
+    atomic_store_explicit(&__sig.pending, 0, memory_order_relaxed);
     // re-enable threads
     __enable_threads();
     // re-apply code morphing for function tracing

libc/proc/getrusage-nt.c

@@ -21,6 +21,7 @@
 #include "libc/calls/struct/rusage.internal.h"
 #include "libc/calls/syscall_support-nt.internal.h"
 #include "libc/fmt/wintime.internal.h"
+#include "libc/intrin/atomic.h"
 #include "libc/nt/accounting.h"
 #include "libc/nt/process.h"
 #include "libc/nt/runtime.h"
@@ -75,7 +76,7 @@ textwindows int sys_getrusage_nt(int who, struct rusage *usage) {
       .ru_majflt = memcount.PageFaultCount,
       .ru_inblock = iocount.ReadOperationCount,
       .ru_oublock = iocount.WriteOperationCount,
-      .ru_nsignals = __sig.count,
+      .ru_nsignals = atomic_load_explicit(&__sig.count, memory_order_acquire),
   };
 
   if (who == RUSAGE_BOTH) {