make pdfview first responder on mouse down, because 10.6 doesn't do that automatically anymore
make pdfview first responder on mouse down, because 10.6 doesn't do that automatically anymore

git-svn-id: cb3fc60f0f557b927b8032d8a94e869b6f9f230b@5650 0fceea05-a30d-0410-8a8b-80ef821fb0a1

camillobruni/skim,camillobruni/skim,jasongrout/skim,camillobruni/skim,camillobruni/skim,jasongrout/skim