Improve Windows Console I/O

- Blocking read operations on the Windows Console can now EINTR
- Blocking read operations on Windows pipes now EINTR more reliably
- setitimer() will no longer be inherited across fork() on Windows
- It's now possible to use ECHO when the console is in raw mode
- The ECHOCTL flag now works correctly on the Windows Console
- The ICRNL flag now works correctly on the Windows Console
- pread() and pwrite() will now raise ESPIPE on Windows
- Opening /dev/tty on Windows is improved (untested)
- Overlapped I/O is now implemented in a better way

tool/build/runit.c

@@ -448,7 +448,7 @@ int SpawnSubprocesses(int argc, char *argv[]) {
       break;
     }
   }
-  CHECK_NE(-1, unlink(tpath));
+  unlink(tpath);
   sigprocmask(SIG_SETMASK, &savemask, 0);
   sigaction(SIGQUIT, &savequit, 0);
   sigaction(SIGINT, &saveint, 0);