bug#7594: 24.0.50; doc string of `line-move-visual'

[Drew Adams]

Doc string:
 
 When non-nil, `line-move' moves point by visual lines.
 This movement is based on where the cursor is displayed on the
 screen, instead of relying on buffer contents alone.  It takes
 into account variable-width characters and line continuation.
 
It says nothing about what happens when the value is nil.  Please fix
that.  In particular, please point out that the nil behavior was the
default behavior before Emacs version 23.blah.
 

In GNU Emacs 24.0.50.1 (i386-mingw-nt5.1.2600)
 of 2010-12-06 on 3249CTO
Windowing system distributor `Microsoft Corp.', version 5.1.2600
configured using `configure --with-gcc (4.4) --no-opt --cflags
-Ic:/imagesupport/include'