Prefer 'x_display_info *' to 'Display *' in X selection code.

Prefer 'x_display_info *' to 'Display *' in X selection code.
This helps to avoid unneeded calls to x_display_info_for_display.
* xterm.h (struct selection_input_event): Record 'x_display_info *'
instead of 'Display *'.
(SELECTION_EVENT_DPYINFO): New macro.
(SELECTION_EVENT_DISPLAY): Now inline function to prohibit using
it as an lvalue.  Mention this in comment.
* xterm.c (handle_one_xevent): Use SELECTION_EVENT_DPYINFO.
* xselect.c (x_get_window_property_as_lisp_data, x_atom_to_symbol)
(selection_data_to_lisp_data, receive_incremental_selection):
Convert to use 'x_display_info *'.  Adjust users where appropriate.
(lisp_data_to_selection_data): Likewise.  Also pass 'struct
selection data *' as last arg to not return values in args.
(unexpect_property_change): Use common removal technique.