Fix wrong return type

Android g++4.8 errors out with

jsapi/qjsvalueiterator.cpp: In member function 'QString QJSValueIterator::name() const':
jsapi/qjsvalueiterator.cpp:155:16: error: converting 'false' to pointer type for argument 1
of 'QString::QString(const char*)' [-Werror=conversion-null]
         return false;

Change-Id: I589418e34c7e1ae72f2bf547067ea8e5944119b8
Reviewed-by: Simon Hausmann <simon.hausmann@digia.com>
Reviewed-by: Paul Olav Tvete <paul.tvete@digia.com>
Reviewed-by: Lars Knoll <lars.knoll@digia.com>
Qt Quick Dialogs: can see and control geometry of QML implementations

QQuickAbstractDialog had x/y/width/height properties already but they
didn't do anything.  It's still not possible with the native dialogs
because neither QPlatformDialogHelper nor QFileDialogOptions etc.
have any geometric properties; but the application author can now
see and control the geometry of any QML dialog implementation.

Change-Id: Icdac9592c72e81175436436027f7fe3d75ff7f42
Reviewed-by: Liang Qi <liang.qi@digia.com>