bug#28008: 25.2; Resume kmacro definition errors C-u C-u <F3>

[Eli Zaretskii]

> From: Tino Calancha <tino.calancha@gmail.com>
> Cc: Eli Zaretskii <eliz@gnu.org>,  28008@debbugs.gnu.org, 
> tino.calancha@gmail.com
> Date: Fri, 11 Aug 2017 21:41:58 +0900
> 
>  ** Patch 1 always save the macro in `last-kbd-macro' after an error or 'C-g'.
>     Then, A. B. and D.2 behaves similarly.
> 
>  ** Patch 2 adds a new variable `last-aborted-kbd-macro': it saves the partial
>     macro there after an error or 'C-g'.  Called `start-kbd-macro' with
>     APPEND non-nil offers to append on `last-aborted-kbd-macro'; possible 
> answers
>     are 'yes', 'no' or 'del' (i.e., append on `last-aborted-kbd-macro' after 
> delete
>     its last character).
> 
>     This is not backward compatible; for instance, the snippets A, B above 
> won't be
>     saved in `last-kbd-macro' (currently they do).
>     It's more tidy; it separates 'good macros', i.e. those ended after
>     'F4' or 'C-x )', from 'partial macros', i.e., those ended after an error 
> or 'C-g'.

All these low-level changes just to support an obscure use case?  Is
really worth the risk to break macros to cater to that?

Thanks.