bug#24713: 26.0.50; edebug-max-depth should be customizable

[Eli Zaretskii]

> From: Gemini Lasswell <gazally@runbox.com>
> Date: Sun, 16 Oct 2016 14:58:44 -0700
> 
> Edebug's recursion limit is currently 150, but this is not enough for
> the following files in the Emacs source tree:
> 
> lisp/calc/calc-ext.el
> lisp/help-macro.el
> lisp/international/fontset.el
> 
> The latter two can be successfully instrumented with edebug-max-depth
> set to 200, but the minimum value necessary for calc-ext.el is somewhere
> between 500 and 1000. All three of these files contain large quoted
> lists.
> 
> I'm attaching a patch to accomplish this.

Thanks, pushed.

A few minor nits for the future:

 . when you add/modify a defcustom, always specify a :version tag
 . please always mention the bug number in the commit log message,
   otherwise it must be added by hand, which is error-prone
 . user-visible changes should be accompanied by suitable changes to
   NEWS and the manuals (I did it this time)
 . please use the US English convention of leaving 2 spaces between
   sentences -- this is what we use in Emacs documentation
 . please configure your Git repo (on Github?) so that your user name
   is identical to what you use to send email, to avoid confusion