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/calls/getrusage-nt.c

@@ -47,6 +47,8 @@ textwindows int sys_getrusage_nt(int who, struct rusage *usage) {
   } else {
     return __winerr();
   }
+  bzero(&memcount, sizeof(memcount));
+  memcount.cb = sizeof(struct NtProcessMemoryCountersEx);
   if (GetProcessMemoryInfo(GetCurrentProcess(), &memcount, sizeof(memcount))) {
     usage->ru_maxrss = memcount.PeakWorkingSetSize / 1024;
     usage->ru_majflt = memcount.PageFaultCount;