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/socket.c

@@ -46,7 +46,7 @@ int socket(int family, int type, int protocol) {
   } else {
     rc = sys_socket_nt(family, type, protocol);
   }
-  STRACE("socket(%s, %s, %s) → %d% m", __describe_socket_family(family),
+  STRACE("socket(%s, %s, %s) → %d% lm", __describe_socket_family(family),
          __describe_socket_type(type), __describe_socket_protocol(protocol),
          rc);
   return rc;