Test failure

[Tor Lillqvist]

> IIRC the reason for that is --headless not really working on
> Windows/Mac, or something like that.

But we already have other tests that cheerfully flash windows on and
off for several minutes when one runs  "make" on Windows and OS X.

Or maybe it's only for "make check"? I don't remember, I nowadays tend
to do "make check" whenever I build after some significant amount of
changes anyway. Anyway, I don't think a few more such tests would
hurt.

Maybe those Writer test should be moved to be done only for "make
check", and enabled for all platforms?

--tml