Fix regression in QJSValueIterator::next() since Qt 5.1.1

Iteration on the form "while (next) { .. }" would skip
the last element.

Change-Id: I50692a5a75e23e423e82b7a39e1892f505e4c612
Reviewed-by: Lars Knoll <lars.knoll@digia.com>

Conflicts:
	src/qml/jsapi/qjsvalueiterator.cpp
Merge pull request #21 from sletta/jsvalueiterator

Fix regression in QJSValueIterator::next() since Qt 5.1.1