Remove port-specific display name lists to avoid extra

Remove port-specific display name lists to avoid extra
complexity and data duplication with display info lists.
* xterm.h (x_display_name_list): Remove declaration.
* xterm.c (x_display_name_list): Remove.
(x_term_init, x_delete_display, syms_of_xterm): Adjust users.
* xfns.c (x_display_info_for_name, Fx_display_list):
Likewise.  Use x_display_list where appropriate.
* w32term.h (w32_display_name_list): Remove declaration.
* w32term.c (w32_display_name_list): Remove.
(w32_initialize_display_info, x_delete_display, syms_of_w32term):
Adjust users.
* w32fns.c (x_display_info_for_name, Fx_display_list):
Likewise.  Use x_display_list where appropriate.
* nsterm.h (ns_display_name_list): Remove declaration.
* nsterm.m (ns_display_name_list): Remove.
(ns_term_init, syms_of_nsterm): Adjust users.
* nsfns.m (ns_display_info_for_name, Fx_display_list):
Likewise.  Use x_display_list where appropriate.
* termhooks.h (TERMINAL_FONT_CACHE): New macro.
* alloc.c (toplevel) [HAVE_WINDOW_SYSTEM]: Include TERM_HEADER.
(mark_terminals): Mark per-terminal font cache.