set verticalsize policy to ignore until we find a better solution. instead of overlap...

set verticalsize policy to ignore until we find a better solution. instead of overlapping dockwidgets we now have a layout where widgets get resized arbitrarily small. in practice this is not an issue since nobody will resize the mainwindow to such small dimension. in the meantime the lyx window will fit nicely on smaller screens. but as said, while looking for something better...

git-svn-id: svn://svn.lyx.org/lyx/lyx-devel/trunk@33839 a592a061-630c-0410-9148-cb99ea01b6c8