[O] temporary directory for export

[Alan Schmitt]

Hello,

I have found how to set a temporary directory for org-babel export files
(using org-babel-temporary-directory), but I cannot find how to specify
that, by default (i.e., unless specified with a "file" option), files
should be exported to a temporary directory.

My motivation for this is that I keep a single folder with many org-mode
files, some of them for presentations, papers, or letters. I regularly
have to go in there and get rid of all the .tex, .log, .pdf, .aux, etc.,
that accumulate.

Thanks,

Alan