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/time.c

@@ -37,13 +37,9 @@ void OpPause(struct Machine *m, uint32_t rde) {
     interactive = isatty(0);
     once = true;
   }
-  if (!IsWindows() && interactive) {
-    pf.fd = 0;
-    pf.events = POLLIN;
-    poll(&pf, 1, 20); /* make spin loops less brutal */
-  } else {
-    sched_yield();
-  }
+  pf.fd = 0;
+  pf.events = POLLIN;
+  poll(&pf, 1, 20); /* make spin loops less brutal */
 }
 
 void OpRdtsc(struct Machine *m, uint32_t rde) {