Rewrite abbrev.c in Elisp.

Rewrite abbrev.c in Elisp.
* image.c (Qcount): Don't declare as extern.
(syms_of_image): Initialize and staticpro `Qcount'.
* puresize.h (BASE_PURESIZE): Increase for the new abbrev.el functions.
* emacs.c (main): Don't call syms_of_abbrev.
* Makefile.in (obj): Remove abbrev.o.
(abbrev.o): Remove.
* abbrev.c: Remove.

Rewrite abbrev.c in Elisp.
* abbrev.el (abbrev-mode): Move custom group from cus-edit.el.
(abbrev-table-get, abbrev-table-put, abbrev-get)
(abbrev-put, make-abbrev-table, abbrev-table-p, clear-abbrev-table)
(define-abbrev, abbrev--check-chars, define-global-abbrev)
(define-mode-abbrev, abbrev--active-tables, abbrev-symbol)
(abbrev-expansion, abbrev--before-point, expand-abbrev)
(unexpand-abbrev, abbrev--write, abbrev--describe)
(insert-abbrev-table-description, define-abbrev-table):
New funs, largely transcribed from abbrev.c.
(abbrev-with-wrapper-hook): New macro.
(abbrev-table-name-list, global-abbrev-table)
(abbrev-minor-mode-table-alist, fundamental-mode-abbrev-table)
(abbrevs-changed, abbrev-all-caps, abbrev-start-location)
(abbrev-start-location-buffer, last-abbrev, last-abbrev-text)
(last-abbrev-location, pre-abbrev-expand-hook, abbrev-expand-function):
New vars, largely transcribed from abbrev.c.
* cus-edit.el (abbrev-mode): Remove.  Move to abbrev.el.
* cus-start.el: Remove abbrev-all-caps and pre-abbrev-expand-hook.
* loadup.el: Load "abbrev.el" before "lisp-mode.el".