Now that overloads are kept ordered, I can replace the existing 
remove_hidden_names fn with ovl_skip_hidden.

The former works by scanning the overloads, then if it discovers a 
hidden one, copying the list (from the beginning) omitting the hidden 
ones.  Now, overloads aren't usually huge, but this forces scanning on 
every lookup, and is O(N^2), so bad.  ovl_skip_hidden simply drops the 
OVL_HIDDEN_P nodes at the start of an overload.  Often doing nothing.

For extra badness, lookup_name_real was applying remove_hidden_names to 
a result that had already had it run!

Applied to trunk.

nathan
-- 
Nathan Sidwell