Move internal QV8QObjectWrapper::newQObject helper to QV4::QObjectWrapper

Change-Id: Ieb1a36ce240b894d19c410b94eccfa79150054c7
Reviewed-by: Lars Knoll <lars.knoll@digia.com>
Move handling of multiply wrapped QObjects from QV8QObjectWrapper into QV4::ExecutionEngine

The bookkeeping is annoying to do, but it should be a rare case. The common case of a
QObject being wrapped only once is still lightweight as-is.

Change-Id: I12e9b67270ca2afbd77b4395246eef0dfc324f8f
Reviewed-by: Lars Knoll <lars.knoll@digia.com>
Removed unused typedef

Change-Id: I17a3fcbbad5169999125aad11ec90cfbd7d4a456
Reviewed-by: Lars Knoll <lars.knoll@digia.com>
Cleanup: Get rid of v8engine pointer in QObjectWrapper

Change-Id: I3a077c6a8ed61ce6dc6a06cf4c4d181509ee8565
Reviewed-by: Lars Knoll <lars.knoll@digia.com>