convert QV8VariantWrapper to v4

Implement variant support through a QV4::VariantObject
class. Port scarce resource support for the
pixmap and image variants.

Change-Id: Ib6aac8debc7f57224ccddb912ab4342c5f1dec15
Reviewed-by: Simon Hausmann <simon.hausmann@digia.com>
Don't GC constructors and prototypes

Change-Id: Iedc894927bc93dc3f5778a4f7855eb3ec37b946b
Reviewed-by: Simon Hausmann <simon.hausmann@digia.com>