Make `window-system' into a keyboard-local variable (rather than

Make `window-system' into a keyboard-local variable (rather than
frame-local as done originally by multi-tty).

* startup.el (window-system): Remove.  Don't make it frame-local.

* keyboard.h (struct kboard): Add Vwindow_system.
* keyboard.c (init_kboard): Set a default for Vwindow_system.
(mark_kboards): Mark Vwindow_system.

* dispnew.c (syms_of_display) <window-system>: Declare terminal-local.
(init_display): Don't set the obsolete `window-system' frame-param.

* xterm.c (x_term_init):
* w32term.c (w32_create_terminal):
* term.c (init_tty): Set Vwindow_system.
* macterm.c (mac_create_terminal): Set a keyboard (missing piece of the
multi-tty merge maybe?), copied from w32term.c.  Set Vwindow_system.

* xfns.c (Fx_create_frame, x_create_tip_frame):
* w32fns.c (Fx_create_frame, x_create_tip_frame):
* macfns.c (Fx_create_frame):
Don't set the obsolete `window-system' frame-param.

* frame.h (Qwindow_system): Remove.
* frame.c (Qwindow_system): Remove.  In `syms_of_frame' as well.
(Fmake_terminal_frame): Don't set obsolete `window-system' frame-param.