* src/xselect.c (x_handle_selection_request): Make sure the type
of a reply to a MULTIPLE request is ATOM_PAIR.

Also, optimize Fx_translate_coordinates to avoid excessive calls
to _XReply.

* lisp/x-dnd.el (x-dnd-get-drop-rectangle): Return empty drop
rectangle if posn-area.
* src/xfns.c (Fx_translate_coordinates): Accept arg
`require_child'.  If not set, allow optimizations based on
cached position data.
* src/xselect.c (x_handle_dnd_message): Use
x_translate_coordinates.
* src/xterm.c (x_translate_coordinates): Export function.
(x_handle_translate_coordinates): New function.
(handle_one_xevent): Fix coding style.
* src/xterm.h: Update prototypes.

* lisp/menu-bar.el (menu-bar-edit-menu): Test buffer-read-only
before gui-backend-selection-exists-p.  This places the less
expensive condition before the more expensive one.
* src/xfns.c (compute_tip_xy): Use cached monitor attributes
whenever available.
(Fx_show_tip): Remove code that really did nothing.
(Fx_backspace_delete_keys_p): Do not download the entire keymap
from the server upon creating a frame.
* src/xmenu.c (create_and_show_popup_menu): Use
x_translate_coordinates_to_root.
(x_menu_show): Use x_translate_coordinates_to_root.
* src/xselect.c (Fx_selection_exists_p): If a temporary
selection owner can be found, use it.
* src/xterm.c (x_translate_coordinates_to_root)
(x_handle_selection_monitor_event, x_find_selection_owner): New
functions.  These functions try to avoid downloading data from
the X server in places that are called very often (i.e. during
tool bar updates.)
(handle_one_xevent): Handle selection notify events.  Also catch
some mistakes found.  Fetch all kinds of key names as well.
(x_create_special_window): New function.
(x_term_init, x_delete_display): Ask for all key names.  Also,
passively monitor selections that are given to
`x-selection-exists-p' during redisplay, so we do not have to
ask the server about them upon each redisplay.
(syms_of_xterm): New variable `x-fast-selection-list'.
* src/xterm.h (struct x_monitored_selection): New structure.
(X_INVALID_WINDOW): New define.
(struct x_display_info): New fields for selection monitoring.
Also, record the fixes extension base.

* src/xselect.c (lisp_data_to_selection_data): Assume an empty
vector represents INTEGER data, instead of blindly trying to
aref it's first element.

* src/xselect.c (receive_incremental_selection): New arg
REAL_BYTES_RET.  Set it to the actual size instead of using the
size of the array after it was grown by xpalloc.
(x_get_window_property_as_lisp_data): Adjust call to
receive_incremental_selection.

Don't say that a value is a fixnum if small enough and a bignum
otherwise, because that is now how Lisp integers always work,
and we generally don't expose the fixnum/bignum difference to the user
unless really necessary.

* src/charset.c (Fencode_char):
* src/editfns.c (Fuser_uid, Fuser_real_uid, Fgroup_gid)
(Fgroup_real_gid, Femacs_pid):
* src/font.c (Ffont_variation_glyphs):
* src/process.c (Fprocess_id):
Edit doc strings.
* src/pgtkselect.c:
* src/xselect.c: Edit comments.

* lisp/cus-start.el (standard): Update defcustom type.
* src/xselect.c (x_should_preserve_selection): New function.
(x_clear_frame_selections): Use it to determine whether or not
to preserve a selection.
* src/xterm.c (x_preserve_selections): Fix tail initialization.
(syms_of_xterm): Update doc string of
`x-auto-preserve-selections'.

* src/frame.c (delete_frame): Bind `x-auto-preserve-selections'
to nil if deleting display.
* src/xselect.c (x_clear_frame_selections): Pass original frame
to that function.
* src/xterm.c (x_preserve_selections): Fix determining the new
owner.
(syms_of_xterm): New defsym `x-auto-preserve-selections'.
* src/xterm.h: Update prototypes.

* lisp/cus-start.el (standard): Add
`x-auto-preserve-selections'.
* src/xselect.c (x_clear_frame_selections): Collect deleted
selections into a variable and preserve them.
* src/xterm.c (x_preserve_selections): New function.
(syms_of_xterm): New variable `x-auto-preserve-selections'.
* src/xterm.h: Update prototypes.