We intend to mark synthetic template parameters (coming from use of auto
parms), as DECL_VIRTUAL_P.  The API of process_template_parm is
awkwardly confusing, and we were marking the previous template parm
(unless this was the first parm).  process_template_parm returns the list
of parms, when most (all?) users really want the newly-added final node.
That's a bigger change, so let's not do it right now.  With this, we
correctly mark such synthetic parms DECL_VIRTUAL_P.

I fell over this trying to update template lambda mangling.  The API of 
process_template_parm is somewhat awkaward, as it returns the whole list, and we 
end up doing a lot of tree_last calls, to get to the newly added node.  I think 
all (or nearly all?) uses could be adapted to it returning the newly added list 
node, but I didn't want to go there right now.

nathan

-- 
Nathan Sidwell