qt: patch for 10.10 compilation issues.

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.

Closes #32215.

Signed-off-by: Mike McQuaid <mike@mikemcquaid.com>