bug#17797: 24.3; Include ert-buffer.el in Emacs

[Stefan Monnier]

> The library 'ert-buffer.el', which does not seem to have a repository
> nor to be included in any package repo, but can easily be found via a
> web-search, offers some fundamental extensions to ERT functionality in
> Emacs core and should thus be included in core.

I don't have a strong opinion either way because I don't know this area
well enough to judge how useful this can be.  So whoever thinks this is
a good or a bad idea, please chime in,


        Stefan