bug#7801: 24.0.50; doc string of `mouse-manu-non-singleton'

[Drew Adams]

Just look at it:
 
"Given menu keymap,
if it defines exactly one submenu, return just that submenu.
Otherwise return the whole menu."

Note the first line, which should be standalone.

In GNU Emacs 24.0.50.1 (i386-mingw-nt5.1.2600)
 of 2011-01-03 on 3249CTO
Windowing system distributor `Microsoft Corp.', version 5.1.2600
configured using `configure --with-gcc (4.4) --no-opt --cflags
-Ic:/imagesupport/include'