bug#13048: 24.3.50; Document Customize type `key-sequence' in Elisp manual

[Drew Adams]

Subject line says it all.  The widget `key-sequence' has been defined
for some time now, and is useful in defcustom :type specs.  But it is
not documented.  It should be, in node `Simple Types'.
 

In GNU Emacs 24.3.50.1 (i386-mingw-nt5.1.2600)
 of 2012-11-19 on MS-W7-DANI
Bzr revision: 110950 monnier@iro.umontreal.ca-20121119182725-5p6w4wjimm7epggr
Windowing system distributor `Microsoft Corp.', version 5.1.2600
Configured using:
 `configure --with-gcc (4.7) --no-opt --enable-checking --cflags
 -Ic:/emacs/libs/libXpm-3.5.10/include -Ic:/emacs/libs/libXpm-3.5.10/src
 -Ic:/emacs/libs/libpng-1.2.37-lib/include -Ic:/emacs/libs/zlib-1.2.5
 -Ic:/emacs/libs/giflib-4.1.4-1-lib/include
 -Ic:/emacs/libs/jpeg-6b-4-lib/include
 -Ic:/emacs/libs/tiff-3.8.2-1-lib/include
 -Ic:/emacs/libs/libxml2-2.7.8-w32-bin/include/libxml2
 -Ic:/emacs/libs/gnutls-3.0.9-w32-bin/include
 -Ic:/emacs/libs/libiconv-1.9.2-1-lib/include'