Dia Windows batch mod

["Rob McDonald" <robm asdl gatech edu>]

I tried to do a

dia foo.dia --filter=mp --export=foo.mp

On dia-0.95-pre1 on Windows.

It crashed with lots of Pango errors.  The first is a GDK_IS_SCREEN
assertion.

I was going to batch convert a bunch of files, but it isn't too important.
Just figured this may not be something that gets lots of testing.

Thanks,

          Rob