[ssaupdate] SSA form updating rewrite

[Daniel Berlin]

> 	* Makefile.in (tree-update-ssa.o): Add.
> 	* lambda-code.c (perfect_nestify): Do not call mark_for_rewrite
> 	and unmark_all_for_rewrite.


This was done to avoid the phi result name being released as we redirect 
an edge and then move phi nodes from one block to another (if you mark 
them for rewrite, it won't release the name), as the comment says.

I don't see anything i nwhat you've done that would change this being 
necessary.