bug#7217: 24.0.50; no doc strings for regexp-opt functions

[Drew Adams]

emacs -Q
 
Please provide doc strings for the so-called "workhorse" regexp-opt
functions.  They are important enough for users that I see them used in
3rd-party libraries.
 
 regexp-opt-group
 regexp-opt-charset
 
To understand these functions, a user needs to read the block comment
for each.  Please move this info to a doc string.
 

In GNU Emacs 24.0.50.1 (i386-mingw-nt5.1.2600)
 of 2010-09-20 on 3249CTO
Windowing system distributor `Microsoft Corp.', version 5.1.2600
configured using `configure --with-gcc (4.4) --no-opt --cflags
-Ic:/imagesupport/include'