bug#18087: 24.4.50; doc string of `kill-region'

[Drew Adams]

This text was added to the doc string for Emacs 24.4:

 The optional argument REGION if non-nil, indicates that we're not just killing
 some text between BEG and END, but we're killing the region.

1. That text should be filled, so the lines are no wider than 70
   columns.

2. The text should say what this "indication" MEANS.  To what or to
   whom are "we" indicating this fact?  And why?  What is the
   USER-VISIBLE EFFECT of a non-nil REGION arg?  Why/when would might
   one want to pass non-nil REGION?  IOW, WHAT IS THIS PARAMETER FOR?

In GNU Emacs 24.4.50.1 (i686-pc-mingw32)
 of 2014-06-28 on ODIEONE
Bzr revision: 117431 rgm@gnu.org-20140628015517-eku6hj8mpgcvfnso
Windowing system distributor `Microsoft Corp.', version 6.1.7601
Configured using:
 `configure --prefix=/c/Devel/emacs/snapshot/trunk
 --enable-checking=yes,glyphs 'CFLAGS=-O0 -g3'
 LDFLAGS=-Lc:/Devel/emacs/lib 'CPPFLAGS=-DGC_MCHECK=1
 -Ic:/Devel/emacs/include''