Decorate overwriting attributes invalid and required in event scope

Looking at the code in org.jboss.seam.ui.renderkit.DecorateRendererBase, doEncodeBegin sets the attributes "required" and "invalid" and
removes them in doEncodeEnd without making an attempt to store away/restore existing values.

This appears to happens with every use of decorate, whether the user refers to the attributes or not, possibly confusing application logic if attributes
with same name have been placed in the event scope.