Don't needlessly duplicate information about the profiler being available
and allow inlining. Use macros to check availability of the profiler
in calling code and generally simplify the code.

Task-number: QTBUG-35315
Change-Id: I0a9daec4a95f74b9db795ef2918a01fb772ea107
Reviewed-by: Michael Brasser <michael.brasser@live.com>
Reviewed-by: Simon Hausmann <simon.hausmann@digia.com>
Reviewed-by: Kai Koehne <kai.koehne@digia.com>