Problems editing cells in NSBrowser (with new test)

[Riccardo Mottola]

Hi,

editing a cell in NSBrowser causes the new value (being edited) to draw 
over the old value.

Fred suggests it might be a problem with the "drawsBackground" setting. 
I did a search on the web but found no clues.

To prove the issue is a pure GUI issue, I made a new testcase for 
GSTest: NSBrowser-test. That shall be helpful in the future anyway, 
tests never hurted :)

Riccardo