Place hardware TTY cursor at the active menu item when displaying a menu.

Place hardware TTY cursor at the active menu item when displaying a menu.

 src/term.c (tty_menu_display): Move the cursor to the active menu
 item.
 (tty_menu_activate): Return the cursor to the active menu item
 after displaying the menu and after displaying help-echo.  See
 http://lists.gnu.org/archive/html/emacs-devel/2014-04/msg00402.html
 for the details of why this is needed by screen readers and
 Braille displays.