bug#6493: 24.0.50; doc strings of region-beginning, region-end

[Drew Adams]

The doc strings just repeat the function names - they provide no helpful
info at all.
 
What we need to add is what is said in the Elisp manual: that the
"beginning" ("end") is the position of either point or the mark,
whichever is smaller (larger).

In GNU Emacs 24.0.50.1 (i386-mingw-nt5.1.2600)
 of 2010-06-21 on 3249CTO
Windowing system distributor `Microsoft Corp.', version 5.1.2600
configured using `configure --with-gcc (4.4) --no-opt --cflags -Ic:/xpm/include'