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

tool/build/lib/ioports.c

@@ -69,11 +69,7 @@ static int OpSerialIn(struct Machine *m, int r) {
         return 0x01;
       }
     case UART_LSR:
-      if (IsWindows()) {
-        p = POLLIN | POLLOUT; /* XXX */
-      } else {
-        if ((p = OpE9Poll(m)) == -1) return -1;
-      }
+      if ((p = OpE9Poll(m)) == -1) return -1;
       s = UART_TTYIDL;
       if (p & POLLIN) s |= UART_TTYDA;
       if (p & POLLOUT) s |= UART_TTYTXR;