Patch qt4 for Yosemite

From upstream patch at https://codereview.qt-project.org/#/c/87515/

This patch changes references to `NSApp` to `[NSApplication sharedApplication]`, since `NSApp` is deprecated on Yosemite. I've excluded the part of the upstream patch against `tests/auto/qfontdialog/tst_qfontdialog_mac_helpers.mm`, since files in `tests/` are not included in release tarballs.