[PATCH] replace call to file(1) with libmagic

[Mark Martinec]

Patrick,

> I threw this onto one of my servers to test, and it was working ok.
> I went ahead and threw in onto 3 large production servers. So far no
> issues. I'll follow up if I get some crashs or something.

Thanks. Works fine here as well.

Did compare timings over a couple of hours, and a typical time
for checking a single simple mail part (which is quite common)
dropped from 27 ms down to 4 ms. With more mail parts (or more
demanding files) the obvious advantage diminishes, but is still
favourable towards calling libmagic directly.

   Mark