Fix various errors in the qjsvalue auto test

Fix various errors in the qjsvalue auto test

Fix creation of Array's from a QStringList
Properly implement toVariant()
Fix VariantObject::toString()
Fix conversion of variant lists to JS values
Remove an XFAIL

Allow comparison of QJSValue objects created from different
engines. There's no reason why we can't simply do this with v4.

Change-Id: I8d8c597dbb032926501508d60bd80622ec964d67
Reviewed-by: Simon Hausmann <simon.hausmann@digia.com>