Stdio.File: Added tcdrain() and tcsetsize(). It is now possible to set the window size for a pty or other terminal. Also adds documentation for them as well as tcflush() and tcsendbreak(), and moves it and the documentation for tc{get,set}attr() from Stdio.File to Stdio.Fd. Also some fixes to make the code work on systems with <sys/termios.h> but no <termios.h>, and preparation to make some of it work on NT. Fixes some of #10013.