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

[Gemini Lasswell]

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. I chose to mention
max-lisp-eval-depth and max-specpdl-size in the defcustom docstring, but
I also noticed that Edebug temporarily bumps max-lisp-eval-depth up by
800 while it's working. I could modify the patch to replace the 800 by
something along the lines of (+ 200 (* max-edebug-depth 4)), if someone
with more Emacs experience than me says it is a good idea. Edebug also
increases max-specpdl-size (by 2000) so that probably would also need to
be changed in the code.

0001-Change-edebug-max-depth-from-defconst-to-defcustom.patch
Description: Text document