revlog: add the appropriate flag is sidedata are passed to `addrevision`

If we need to store sidedata, we need the flag to be set and the associated
processing to be called.

Differential Revision: https://phab.mercurial-scm.org/D6894

mercurial/revlog.py

@@ -1865,6 +1865,8 b' class revlog(object):'
             raise error.ProgrammingError(
                 _("trying to add sidedata to a revlog who don't support them")
                 )
+        else:
+            flags |= REVIDX_SIDEDATA
 
         if flags:
             node = node or self.hash(text, p1, p2)