Remove two more places where we used v8

Change Value::isInt32() to convert to an integer if possible.
Use this to avoid casting doubles to ints twice. usage of
v8::Value::IsInt32() in two places.

Change-Id: I5b9d8be7d90b461c11440bf54660ceef7e8f0f1b
Reviewed-by: Simon Hausmann <simon.hausmann@digia.com>
Remove v8 API usage in qquickitem

Change-Id: Iddea91433afaa7f269c66294a500465bd53c40cd
Reviewed-by: Simon Hausmann <simon.hausmann@digia.com>
Remove v8 usage from qquickglobal

Change-Id: I75c803d8dd997703b64f5b75226d76cf498d03d3
Reviewed-by: Simon Hausmann <simon.hausmann@digia.com>