Replace explicit surrogate handlers by inline methods of QChar class

Replace explicit surrogate handlers by inline methods of QChar class

Merge-request: 1284
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@nokia.com>
(cherry picked from commit 50af55095afe1ba048dde357b771485ef2188778)

Change-Id: I0b1967145ad62243afc2060a6ae4ca141a9609fd
Reviewed-on: http://codereview.qt-project.org/4587
Reviewed-by: Qt Sanity Bot <qt_sanity_bot@ovi.com>
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@nokia.com>