Move walk_tree improvement to 3.3 branch

[Geoffrey Keating]

I just moved:

2003-01-30  Richard Henderson  <rth@redhat.com>

         * tree-inline.c (walk_tree): Streamline duplicate hash table 
lookup.

to the 3.3 branch, since it's a speed improvement.
-- 
Geoff Keating <geoffk@apple.com>