Fix CoreText performance note on OS X 10.9 (Mavericks).

Upstream Qt bug: https://bugreports.qt-project.org/browse/QTBUG-32789
Upstream patch: https://codereview.qt-project.org/#patch,all,70097,4.
Upstream commit: https://qt.gitorious.org/qt/qt/commit/98352b964f

https://github.com/ariya/phantomjs/issues/11418
Fix warning of obsolete userSpaceScaleFactor on OS X 10.9 (Mavericks).

Related upstream bug: https://bugreports.qt-project.org/browse/QTBUG-28574

Issue #1162 https://github.com/ariya/phantomjs/issues/11612