[core] support implicit object 'component' in renderers where getRendersChildren is true

[Martin Koci]

Hi,

problem described in MYFACES-3157 applies for all cases where renderer
reads property from child component. I think that only correct way in
push child to EL before:

child.pushComponentToEL()
Object value = child.getValue();
String style = child.getStyle();
child.popComponentFromEL()

Is that ok? This affects about 8 renderers in myfaces-impl/shared

Kočičák