bug#12727: 24.2.50; please format the doc string of `substitute-command-keys'

[Drew Adams]

Please format the doc string, wrapping the long line. In general, some
of the paragraphs or at least some of their sentences, should be filled.
 
In GNU Emacs 24.2.50.1 (i386-mingw-nt5.1.2600)
 of 2012-10-22 on DANI-PC
Bzr revision: 110618 monnier@iro.umontreal.ca-20121022132928-232zm0fecassmhfb
Windowing system distributor `Microsoft Corp.', version 5.1.2600
Configured using:
 `configure --with-gcc (4.7) --no-opt --enable-checking --cflags
 -I../../libs/libxpm-3.5.8/include -I../../libs/libxpm-3.5.8/src
 -I../../libs/libpng-1.4.10 -I../../libs/zlib-1.2.6
 -I../../libs/giflib-4.1.4-1/include -I../../libs/jpeg-6b-4/include
 -I../../libs/tiff-3.8.2-1/include
 -I../../libs/libxml2-2.7.8-w32-bin/include/libxml2
 -I../../libs/gnutls-3.0.16/include
 -I../../libs/libiconv-1.14-2-mingw32-dev/include'