copy_text_properties.
* textprop.c (copy_text_properties): New function, from David
Gillespie.
* intervals.h: Declare copy_text_properties.
* fns.c: #include "intervals.h".
(Fsubstring): Copy text properties to result string.
(concat): Copy text properties to result string.
* ymakefile (fns.o): Note that this depends on INTERVAL_SRC.
(OVERLAYP): New predicate.
(CHECK_OVERLAY): New type-checker.
(Qoverlayp): New extern declaration.
* buffer.c (Foverlayp): New function.
(Qoverlayp): New atom.
(overlays_at, recenter_overlay_lists): Abort if we encounter an
invalid overlay.
(syms_of_buffer): defsubr Soverlayp; initialize Qoverlayp.
(Fdelete_overlay): Set the overlay's markers to point nowhere.
Use CHECK_OVERLAY instead of signalling a special error.
(Fmove_overlay, Foverlay_put): Use CHECK_OVERLAY instead of
signalling a special error.
(Foverlay_get): Use CHECK_OVERLAY.
* fns.c (internal_equal): Define this for overlays.
* buffer.h (OVERLAY_VALID): Define in terms of OVERLAYP.
* print.c (print): Give overlays their own print syntax.
* alloc.c (mark_object): Treat overlays like conses.
* lread.c (read_filtered_char): New function, which contains the
code which used to be in Fread_char, Fread_event, and
Fread_char_exclusive; there was a lot of common code.
(Fread_char, Fread_event, Fread_char_exclusive): Rewrite in terms
of read_filtered_char.
* lisp.h (read_filtered_char): Declare this extern here.
* fns.c (Fy_or_n_p): Call read_filtered_char, arranging to delay
switch-frame events.
floating-point as well as integer arguments. subr.el defines the
former as an alias for the latter.
* data.c (Fnumber_to_string): Renamed from Fint_to_string.
(wrong_type_argument): Adjust caller.
(syms_of_data): Adjust defsubr.
* fns.c (concat): Adjust caller.
* lisp.h (Fnumber_to_string): Adjust extern declaration.
* mocklisp.c (Finsert_string): Adjust caller.
* process.c (status_message): Adjust caller.
