Add default parameter value for ScopedCallData()

Change-Id: I16b6662a47c682e145d3e2201f9e90f58405a599
Reviewed-by: Simon Hausmann <simon.hausmann@digia.com>
Add default parameter value for ExecutionEngine::newString()

Change-Id: I8efbfb07ea61e2c6d03eeb79671006d209e4d48e
Reviewed-by: Simon Hausmann <simon.hausmann@digia.com>