PATCH: use hashval_t in tree.h

[Daniel Berlin]

On Thu, 2006-04-27 at 10:41 +1000, Ben Elliston wrote:
> iterative_hash_expr prototyped in tree.h takes (and returns) a
> hashval_t, yet tree.h cheats and uses unsigned int, knowing the basic
> type of hashval_t.  If hashval_t's type ever changes, this may break.
> 
> Tested with a bootstrap on i686-pc-linux-gnu.  Okay for the trunk?

Not without updating the makefile dependencies it's not :)