Fix fullscreen for xpdf (at least on debian, with proper _NET_WM_STATE hints)

Fix fullscreen for xpdf (at least on debian, with proper _NET_WM_STATE hints)

xpdf sets the _NET_WM_STATE before actually mapping the window. i3 only checked
for changes of this hint, but not if it is already set when intially managing
the window.

Note that you need to patch your xpdf to support _NET_WM_STATE, because, while
only being reported at 2004, upstream still did not merge the patch *grrr*
See this debian bug report:
http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=247602
Or directly download the patch from:
http://bugs.debian.org/cgi-bin/bugreport.cgi?msg=61;filename=31_fullscreen.dpatch;att=1;bug=247602