Comment 2 for bug 412367

A major problem with this approach is that we are currently using the current block ID to label SSA variables. With this approach, we can't name them the correct name.

(Internally, cfg.ref_id is now meaningless and all dependencies on it -- now solely in ast_cfg -- need to be removed.)

We'll probably have to change ast_cfg so it generates names unique to the function, not the block, and don't involve the block ID in naming the variable at all.