Make fork() go 30% faster

This change makes fork() go nearly as fast as sys_fork() on UNIX. As for
Windows this change shaves about 4-5ms off fork() + wait() latency. This
is accomplished by using WriteProcessMemory() from the parent process to
setup the address space of a suspended process; it is better than a pipe

libc/sock/kntwsadata.c

@@ -51,3 +51,7 @@ textwindows void WinSockInit(void) {
     _Exit(1);
   }
 }
+
+textwindows dontinstrument void WinSockFork(void) {
+  WSAStartup(VERSION, &kNtWsaData);
+}