Make improvements for Actually Portable Emacs

- Get SIGWINCH working again on the New Technology
- Correctly handle O_NOFOLLOW in open() on Windows
- Implement synthetic umask() functionality on Windows
- Do a better job managing file execute access on Windows
- Fill in `st_uid` and `st_gid` with username hash on Windows
- Munge UNICODE control pictures into control codes on Windows
- Do a better job ensuring Windows console settings are restored
- Introduce KPRINTF_LOG environment variable to log kprintf to a file

libc/log/die.c

@@ -55,10 +55,10 @@ relegated wontreturn void __die(void) {
       DebugBreak();
     }
     ShowBacktrace(2, __builtin_frame_address(0));
-    _Exitr(77);
+    _Exit(77);
   } else if (owner == me) {
     kprintf("die failed while dying\n");
-    _Exitr(79);
+    _Exit(79);
   } else {
     _Exit1(79);
   }