more: Read keystrokes from stdout instead of trying to re-open it

If we're running more on a TTY that we don't have filesystem access to,
we can't rely on open(ttyname(STDOUT_FILENO)). Since all the stdio fd's
are opened read/write anyway, we can just read from stdout, even if it
feels a bit weird. :^)

Userland/more.cpp

@@ -50,11 +50,7 @@ int main(int argc, char** argv)
  return 1;
  }
 
- key_fd = open(ttyname(1), O_RDONLY);
- if (key_fd < 0) {
- perror("open");
- return 1;
- }
+ key_fd = STDOUT_FILENO;
 
  struct winsize ws;
  ioctl(1, TIOCGWINSZ, &ws);