In case somebody uses QVector as a stack, it is not fair to have
takeLast, removeLast and pop_back to do way too much work.
This is still very slow compared to std::vector::pop_back
(mostly due implicit sharing), however it is more than a
factor faster than before.
Change-Id: I636872675e80c8ca0c8ebc94b04f587a2dcd6d8d
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>