Misc manual updates.

Misc manual updates.

* doc/emacs/package.texi (Package Installation): Document use of
package-initialize in init file.

* doc/lispref/os.texi (Startup Summary): Mention package loading.
(Init File): Don't refer to .emacs in section title.  Copyedits.
(Terminal-Specific): Give a realistic example.
(Command-Line Arguments): Reference Entering Emacs instead of
repeating the spiel about not restarting Emacs.
(Time of Day): Discuss time representation at beginning of node.
(Sound Output): Copyedits.

* doc/lispref/package.texi (Packaging Basics): Document package-initialize.