org-latex.el: New defcustom `org-export-latex-quotes' to control quotes.
* org-latex.el (org-export-latex-quotes): New defcustom.
(org-export-latex-quotation-marks): Use it.
This allows users to define what quotes they want to use as a
replacement of english double-quotes while exporting to LaTeX.
In particular, if you use the csquote package, you can configure
Org to output something like \endquote{some quoted text} instead
of "some quoted text".
Thanks to Frederik for bringing this issue up, and to Thomas S.
Dye, Nick Dokos and Stefan Nobis for elaborating this solution.