(x_focus_changed, x_detect_focus_change): Remove

(x_focus_changed, x_detect_focus_change): Remove
numchars arg.  Always store event into bufp arg.  Return nothing.
Callers changed accordingly.
(glyph_rect): Simplify.
(STORE_KEYSYM_FOR_DEBUG): New macro.
(SET_SAVED_MENU_EVENT): Use inev instead of bufp, etc.
(current_bufp, current_numcharsp) [USE_GTK]: Remove.
(current_hold_quit) [USE_GTK]: Add.
(event_handler_gdk): Adapt to new handle_one_xevent.
(handle_one_xevent): Remove bufp_r and numcharsp args.
Add hold_quit arg. Rework to use just one, local, inev
input_event. Store inev directly in fifo using
kbd_buffer_store_event_hold.  Update count in one place.
Postpone call to gen_help_event until inev is stored; use new
local do_help for this.
Simplify handling of keysyms (consolidate common code).  Fix bug
where count was updated with nchars instead of nbytes.
Remove local emacs_event in handing of ButtonPress event; just use
inev instead (so no reason to copy it later).
Remove `out' label.  Rename label `ret' to `done'; add various
`goto done' to clarify code flow in deeply nested blocks.
(x_dispatch_event): Simplify as handle_one_xevent now calls
kbd_buffer_store_event itself.
(XTread_socket): Remove bufp_r and numcharsp args. Add hold_quit
arg.  Call handle_one_xevent with new arglist.  Store event from
x_session_check_input in fifo.
[USE_GTK]: Setup current_hold_quit.
Decrement handling_signal before unblocking input.
(x_initialize) [USE_GTK]: Initialize current_count.