Make read() and write() signal handling atomic

You would think this is an important bug fix, but unfortunately all UNIX
implementations I've evaluated have a bug in read that causes signals to
not be handled atomically. The only exception is the latest iteration of
Cosmopolitan's read/write polyfill on Windows, which is somewhat ironic.

libc/sock/connect-nt.c

@@ -146,7 +146,7 @@ textwindows static int sys_connect_nt_impl(struct Fd *f, const void *addr,
     // check if we still need more time
     if (!ready) {
       if (f->flags & O_NONBLOCK) {
-        return ealready();
+        return etimedout();
       } else {
         continue;
       }