Rework quoting in tutorial

Rework quoting in tutorial

* doc/lispintro/emacs-lisp-intro.texi (Sample let Expression)
(if in more detail, type-of-animal in detail, else): Rework the
early example to use " rather than ' so that we don’t burden
complete novices with the low-priority detail of text quoting style.
(Complete zap-to-char, kill-region, Complete copy-region-as-kill)
(kill-new function, kill-ring-yank-pointer)
(Complete forward-sentence, Loading Files)
(Code for current-kill, Code for current-kill, yank):
Resurrect the Emacs 22 versions of the code, which uses grave
quoting style in doc strings.
(Complete zap-to-char): Mention how quoting works in doc strings.