Wrap calls to Sequence::push_back

Wrap calls to Sequence::push_back

In C++11 push_back is overloaded to support rvalue-references,

   void std::vector<T>::push_back(const T &);
   void std::vector<T>::push_back(T &&);

so attempting to get the address for push_back is ambiguous.

Instead of hardcoding the function signature, the better and more
general solution is to allow the compiler to do the required overload
resolution itself, also allowing for implicit conversions to take place.

Task-number: QTBUG-18996
Done-with: Liang Qi
Reviewed-by: Olivier Goffart
(cherry picked from commit ca34cc75294e0d2a8bc491a2c679fe8a69cd0408)

Change-Id: Id271118e489f888905e491dd4cfc3d2db7697552
Reviewed-on: http://codereview.qt-project.org/4642
Reviewed-by: Liang Qi <liang.qi@nokia.com>
Reviewed-by: Qt Sanity Bot <qt_sanity_bot@ovi.com>