Improve synchronization

- Fix bugs in kDos2Errno definition
- malloc() should now be thread safe
- Fix bug in rollup.com header generator
- Fix open(O_APPEND) on the New Technology
- Fix select() on the New Technology and test it
- Work towards refactoring i/o for thread safety
- Socket reads and writes on NT now poll for signals
- Work towards i/o completion ports on the New Technology
- Make read() and write() intermittently check for signals
- Blinkenlights keyboard i/o so much better on NT w/ poll()
- You can now poll() files and sockets at the same time on NT
- Fix bug in appendr() that manifests with dlmalloc footers off

libc/sock/shutdown.c

@@ -40,6 +40,6 @@ int shutdown(int fd, int how) {
   } else {
     rc = ebadf();
   }
-  STRACE("shutdown(%d, %d) -> %d% m", fd, how, rc);
+  STRACE("shutdown(%d, %d) -> %d% lm", fd, how, rc);
   return rc;
 }