bug#32430: 26; Elisp manual: Please consider indexing each char class

[Drew Adams <drew.adams@oracle.com>]

I wanted to go to the Elisp manual section that specifies char-class
[:blank:].  I tried `i blank', even with substring matching.  Not
recalling that such critters are called "character classes" I just used
`i regexp' (with substring matching) to find entry "character classes in
regexp".

So not a big problem (assuming you have substring matching).  But I
think it would be helpful to add entries such as these (which don't
require substring matching):

ascii character class, regexp
alnum character class, regexp
alpha character class, regexp
blank character class, regexp
...

(Even better would be to allow :blank: etc. and [:blank:] instead of
just blank etc., but I seem to recall that Info won't allow such entries.)

In GNU Emacs 26.1 (build 1, x86_64-w64-mingw32)
 of 2018-05-30
Repository revision: 07f8f9bc5a51f5aa94eb099f3e15fbe0c20ea1ea
Windowing system distributor `Microsoft Corp.', version 10.0.16299
Configured using:
 `configure --without-dbus --host=x86_64-w64-mingw32
 --without-compress-install 'CFLAGS=-O2 -static -g3''