Fix crashes in workerscript tests (qqmlecmascript and qquickworkerscript)

We need access to the QNam for a worker and other bits from the v8Engine,
so for that it's easiest right now to store the v8engine pointer directly.

There aren't many occurrences of v8engine left and we're gradually getting rid
of them, but this let's the tests not crash at least :). Once the transition
is complete, QV8Engine should collapse and v4->v8Engine->jsengine should become
v4->publicEngine again.

Change-Id: I98558dd687875f20f1dbe25381ee7efe502c7f24
Reviewed-by: Lars Knoll <lars.knoll@digia.com>
Move QV8QObjectWrapper::newQObject into QV4::QObjectWrapper

...where it is just called wrap(), because it doesn't always create a new
JS wrapper for the QObject.

Change-Id: Ieed0fc97174eb51cd04df0149e715c234a5822bd
Reviewed-by: Lars Knoll <lars.knoll@digia.com>
Improve type error messages when reading properties

This fixes the expected output of the qobjectConnectionListExceptionHandling and
while we're at it this patch also re-enables the importScripts test. The test
expects similar output that now passes. importScripts_data produces two failures
though, that are unrelated to expected error message but indicate real bugs.

Change-Id: I606b8791524d19a4bb20a81c30abc2285a1a0a0f
Reviewed-by: Lars Knoll <lars.knoll@digia.com>
Get rid of the QV8Engine pointer in QV8QObjectConnectionList

Change-Id: I06ee7afb9abd81a354d84d312be9ea90b91d9baf
Reviewed-by: Lars Knoll <lars.knoll@digia.com>