Improve Windows Console I/O

- Blocking read operations on the Windows Console can now EINTR
- Blocking read operations on Windows pipes now EINTR more reliably
- setitimer() will no longer be inherited across fork() on Windows
- It's now possible to use ECHO when the console is in raw mode
- The ECHOCTL flag now works correctly on the Windows Console
- The ICRNL flag now works correctly on the Windows Console
- pread() and pwrite() will now raise ESPIPE on Windows
- Opening /dev/tty on Windows is improved (untested)
- Overlapped I/O is now implemented in a better way

libc/runtime/fork-nt.c

@@ -68,6 +68,7 @@ __static_yoink("_check_sigchld");
 
 extern int64_t __wincrashearly;
 bool32 __onntconsoleevent_nt(uint32_t);
+void sys_setitimer_nt_reset(void);
 void kmalloc_unlock(void);
 
 static textwindows wontreturn void AbortFork(const char *func) {
@@ -396,6 +397,10 @@ textwindows int sys_fork_nt(uint32_t dwCreationFlags) {
     if (ftrace_stackdigs) {
       _weaken(__hook)(_weaken(ftrace_hook), _weaken(GetSymbolTable)());
     }
+    // reset alarms
+    if (_weaken(sys_setitimer_nt_reset)) {
+      _weaken(sys_setitimer_nt_reset)();
+    }
   }
   if (untrackpid != -1) {
     __releasefd(untrackpid);