TTY Support for ECMA-48 strike-through graphic rendition

TTY Support for ECMA-48 strike-through graphic rendition

* term.c: Support strike-through in capable terminals.
(no_color_bit): Replace unused NC_INVIS with
NC_STRIKE_THROUGH.
(turn_on_face): Output via TS_enter_strike_through_mode
if available.
(turn_off_face): Handle strike-through case.
(tty_capable_p, init_tty): Support strike-through.
* termchar.h (struct tty_display_info): Add field for
strike-through.
* xfaces.c (tty_supports_face_attributes_p, realize_tty_face):
Handle strike-through case.
* dispextern.h: Add TTY_CAP_STRIKE_THROUGH definition.
(struct face): Add field tty_strike_through_p.