Improve documentation strings and prompts in abbrev.el

Improve documentation strings and prompts in abbrev.el

* lisp/abbrev.el (abbrev-file-name, only-global-abbrevs)
(copy-abbrev-table, insert-abbrevs, list-abbrevs)
(abbrev-table-name, edit-abbrevs, define-abbrevs)
(read-abbrev-file, quietly-read-abbrev-file, write-abbrev-file)
(abbrev-edit-save-to-file, abbrev-edit-save-buffer)
(add-mode-abbrev, add-global-abbrev, inverse-add-mode-abbrev)
(inverse-add-global-abbrev, abbrev-prefix-mark)
(expand-region-abbrevs, abbrev-table-get, abbrev-table-put)
(abbrev-get, abbrev-minor-mode-table-alist, abbrevs-changed)
(abbrev-all-caps, last-abbrev-text, last-abbrev-location)
(clear-abbrev-table, define-abbrev, define-global-abbrev)
(define-mode-abbrev, abbrev--active-tables, abbrev--symbol)
(abbrev-symbol, abbrev-expansion, abbrev-insert)
(abbrev-expand-function, abbrev--suggest-above-threshold)
(abbrev--suggest-saved-recommendations)
(abbrev--suggest-shortest-abbrev, abbrev--suggest-get-totals)
(insert-abbrev-table-description, define-abbrev-table)
(abbrev-table-menu): Fix doc strings: wording, punctuation,
clarity.
(add-abbrev, inverse-add-abbrev): Improve the prompt text.
(Bug#55527)