How check when symbol is introduced in Emacs?

[Oleksandr Gavenko <gavenko@bifit.com.ua>]

Usually I get Error with previous Emacs version when symbol is undefined.

To workaround I use code like:

(when (or (>= emacs-major-version 23)
                   (and (= emacs-major-version 22) (>= 
emacs-minor-version 2)))
    (setq 'symb val)
   )

But I must know low limit of version to get better code.

Previously I put version when Emacs don;t fail.

Next I learn to search ChangeLog.

Next I learn use bzr repo with C-x v g and pressing a lot of 'A' command but
it to hard understand which revision goes to release.

Some symbol have properties like :version "20.4". I use it.

Please recommend another simple way or point to docs!