(Setting up a customization file): Grammar fix.

(Setting up a customization file): Grammar fix.
Customize is no longer "new".
(Displaying the current line or column): Line-number mode is on by
default.  Don't mention `column' package.  Mention linum.el.
(Turning on abbrevs by default): Explain how to do it for buffers,
modes, and everywhere.
(Associating modes with files): Use add-to-list.  Don't mention Emacs 19.
(Highlighting a region): On by default since 23.1.
(Replacing highlighted text): Update doc quote.
(Working with unprintable characters): Don't mention search-quote-char.
(Using an already running Emacs process): Gnuclient is probably not an
enhancement these days.
(Indenting switch statements): Remove mention of pre-Emacs 20.
(Horizontal scrolling): Abbreviate Emacs 20 description.
(Replacing text across multiple files): Fix name of dired command.
(Disabling backups): Use require not load.