Cleanups in qv4stringobject

Make the methods GC clean, and simplify some logic

Change-Id: I02df8cb571f27d640c6effc871ea7c24b23b8368
Reviewed-by: Simon Hausmann <simon.hausmann@digia.com>
Fix Persistent/WeakValue API

Don't use unprotected Values in the API anymore.

Change-Id: I8851628227fca374de24701bc8ee0908b5ae3923
Reviewed-by: Simon Hausmann <simon.hausmann@digia.com>
Fix API of QQmlV4Handle

Change-Id: Iac4a3fefebd33a5990408598486231a5add8e639
Reviewed-by: Simon Hausmann <simon.hausmann@digia.com>
Fix QQmlV4Function API to be GC safe

Change-Id: Id4f79c22fc48ada1c8a9a858e1b7b3d1cf14d120
Reviewed-by: Simon Hausmann <simon.hausmann@digia.com>
Make parts of qv8engine_p.h GC safe

Change-Id: Iaa15423cedc307a09b3cd7287272d93d7a604caf
Reviewed-by: Simon Hausmann <simon.hausmann@digia.com>
Move more API over to use ValueRef

Change-Id: I372f1f3e3e78d45912a913f437e622e0acfc9646
Reviewed-by: Simon Hausmann <simon.hausmann@digia.com>
Convert more methods in QV8Engine

Change-Id: I5b059b41842b4a6d9541525b3955d2b64c0011c3
Reviewed-by: Simon Hausmann <simon.hausmann@digia.com>
Skip two tests that don't work reliably with a conservative GC

Change-Id: I5619d533b6e48c88fda063bc7cdcc62d6838bcdf
Reviewed-by: Simon Hausmann <simon.hausmann@digia.com>