Make sure functions returning iterators have an iterator as parameter

Make sure functions returning iterators have an iterator as parameter

The IA-64 C++ ABI does not encode the return type for non-template
functions (QVector is the template, not the function), which means that
these two functions have the same signature:

  Node *QVector<Node>::begin()
  typename class QTypedArrayData<Node>::iterator QVector<Node>::begin()
  [both are _ZN7QVectorI4NodeE5beginEv]

When linking compilation units compiled with different
QT_STRICT_ITERATORS settings, only one of the two out-of-line copies
will survive. Depending on the ABI, we may have a problem: the ABI can
say that a function returning a structure takes an implicit first
parameter, which a function returning a regular pointer doesn't.

Task-number: QTBUG-27277
Change-Id: I57a59e5a7c46f55faabfe85c073dca89d2a7bbf3
Reviewed-by: Jan Kundrát <jkt@flaska.net>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>