Checked lispref/abbrevs.texi

Checked lispref/abbrevs.texi

* doc/lispref/abbrevs.texi: Small copyedits throughout.
(Abbrev Mode): Remove this section, folding it into the top-level.
(Abbrev Tables): Don't mention irrelevant return values.
(Abbrev Expansion): Add cross-ref for wrapper hooks.
(Standard Abbrev Tables): Emacs Lisp mode now has its own table.
(Abbrev Table Properties): Update nil :regexp description.

* lisp/abbrev.el (copy-abbrev-table, abbrev-table-p)
(abbrev-minor-mode-table-alist, define-abbrev, abbrev-insert)
(expand-abbrev, define-abbrev-table): Doc fixes.

* admin/FOR-RELEASE: Related markup.