Use -fPIE if required by Qt.
Workaround bug in Qt 5.0.0 to 5.0.3 QStandardItemModel.

The commit in qtbase 9dfba89c (Add implementations of QAIM::sibling
in public APIs., 2012-09-26) added a buggy implementation of sibling(),
and the commit f136701b (Use the base implementation of
QAbstractItemModel::sibling in QSIM., 2013-02-21) resolves it.
Merge topic 'qt5-fixes' into next

1643b65 Workaround bug in Qt 5.0.0 to 5.0.3 QStandardItemModel.
0918f21 Use -fPIE if required by Qt.