Fix crashes in `delete-terminal' caused by recursive calls or X displays with live...

Fix crashes in `delete-terminal' caused by recursive calls or X displays with live frames.

* src/termhooks.h (terminal) <deleted>: New member.

* src/term.c (delete_tty): Use it.
  (deleting_tty): Remove old variable.

* src/terminal.c (delete_terminal): Use terminal->deleted.

* src/xterm.c (x_delete_terminal): Use terminal->deleted.  Delete all
  frames on the display explicitly.

git-archimport-id: lorentey@elte.hu--2004/emacs--multi-tty--0--patch-562