V4 string table cleanups

Move the string table (index and data) to the end of the compilation unit.
That makes it easier to extend the string table later with new strings - for
example when transitioning from JS data to an entire QML unit - because all the
other offsets within the JS data remain the same.

Change-Id: Ib28caf943ee2ec74b7acc19c2980de0853bb8086
Reviewed-by: Lars Knoll <lars.knoll@digia.com>
Fix crash in conversion from QVariantMap to QJSValue

When the key is an array index, use arraySet instead of trying to insert
an array index as internal class member.

Task-number: QTBUG-37854
Change-Id: I23f01cc9d6be98b57d3f13ac7ee847298e9632a3
Reviewed-by: Matt Broadstone <mbroadst@gmail.com>
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@digia.com>