The method signature of PropObj::pushProp()
has changed.
Old: extend public bool pushProp(str key, PropObj z, Object env=null, StrBuf error=null) { New: extend public bool pushProp(str key, PropObj z, Object env=null, StrBuf error=null, PushPropsEnv receiverEnv=null, PushPropsEnv pusherEnv=null) {