use * for pointer type instead of &

See #770

To help automatically translate code, see the
zig-fmt-pointer-reform-2 branch.

This will convert all & into *. Due to the syntax
ambiguity (which is why we are making this change),
even address-of & will turn into *, so you'll have
to manually fix thes instances. You will be guaranteed
to get compile errors for them - expected 'type', found 'foo'

src-self-hosted/scope.zig

@@ -1,6 +1,6 @@
 pub const Scope = struct {
     id: Id,
-    parent: &Scope,
+    parent: *Scope,
 
     pub const Id = enum {
         Decls,