Reduce QtCore lib binary size by around ~3KB, by removing template code

Reduce QtCore lib binary size by around ~3KB, by removing template code

Reusing a template is much better then creating a new one, even if it
should inline the same code.

For some reason replacing T* by void* force gcc to remove a few bytes
per template instantiation too, it is not really significant, but it
alows us to simplify the code.

Benchmarks don't show any regressions.

Change-Id: I4fdf1e4dc311b23021eb5758605602937d05b183
Reviewed-by: Bradley T. Hughes <bradley.hughes@nokia.com>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>