bug#64517: Looking for manuals in Info within Emacs

[uzibalqa]

Currently looking for manuals in Info within emacs is not so straightforward.

The following gets you to the elisp reference manual

   C-h i m elisp

So why not also have the following for accessing the elisp intro

   C-h i m elisp intro        ; (instead of "C-h i m emacs lisp intro")

This would improve naming consistency "elisp" is the reference, "elisp intro"
is the intro.

I further suggest having

   C-h i m emacs manual
   C-h i m elisp manual
   C-h i m elisp intro manual

So that everybody will know it is a reference to manuals.