Fix use of @key in Texinfo manuals

Fix use of @key in Texinfo manuals

* doc/misc/efaq-w32.texi (Location of init file):
* doc/misc/org.texi (Editing source code, Export settings)
(Closing items, Drawers, Structure editing):
* doc/misc/gnus.texi (Spam and Ham Processors, Terminology):
* doc/misc/calc.texi (Keypad Functions Menu, Keypad Binary Menu)
(Keypad Vectors Menu, Keypad Main Menu, Basic Arithmetic)
(Symbolic Mode):
* doc/misc/sc.texi (Electric References):
* doc/misc/info.texi (Help-^L):
* doc/misc/reftex.texi (Reference Styles):
* doc/misc/idlwave.texi (Troubleshooting, Examining Variables)
(Lesson III---User Catalog, Using the Shell):
* doc/misc/eshell.texi (Bugs and ideas):
* doc/misc/ada-mode.texi (Automatic Casing):
* doc/misc/ediff.texi (Selective Browsing):
* doc/misc/vip.texi (Customizing Constants):
* doc/misc/pcl-cvs.texi (Selected files):
* doc/misc/efaq.texi (Replying to the sender of a message)
(Basic keys, No Meta key, Matching parentheses)
(Origin of the term Emacs, Installing Texinfo documentation)
(Learning how to do something, Emacs manual, Extended commands):
* doc/misc/viper.texi (Rudimentary Changes):
* doc/misc/tramp.texi (Frequently Asked Questions):
* doc/emacs/kmacro.texi (Basic Keyboard Macro):
* doc/emacs/frames.texi (Frame Commands):
* doc/emacs/msdos.texi (Windows Keyboard):
* doc/emacs/search.texi (Query Replace):
* doc/lispintro/emacs-lisp-intro.texi (Keybindings)
(Note for Novices):
* doc/lispref/tips.texi (Key Binding Conventions): Fix use of
@key.  For the details, see
http://lists.gnu.org/archive/html/emacs-devel/2018-04/msg00390.html.