[texworks] hide preview window from window manager

[Stefan Witzel]

Thank you for your replies, Bruno and Paul! To illustrate my point I 
have uploaded screenshots at

   http://dl.dropbox.com/u/6283205/texworks.tar.gz

The first picture shows what the panel bar looks like and the second is 
how I would like it to look even if the same windows are open.
My problem is not just about finding the correct texworks window 
(actually I think the first one is always the source code and the second 
the pdf). But I might for example open some other windows (say a 
browser, a file manager and a console) and then it is inconvenient if 
the several texworks windows already crowd the panel all by themselves.

Best,
Stefan