RFC: don't cache objects larger than X

[Jason A. Donenfeld]

I face this same problem, in fact. Unless somebody beats me to it, I'd
be interested in giving this a stab.

One issue is that cache entries are currently "streamed" into the
cache files, as they're produced. It's not trivially possible to know
how big it's going to be beforehand. This means that the best we could
do would be to just immediately unlink it after creation and printing.
Would this be acceptable?

Regards,
Jason