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'

test/cases/incomplete_struct_param_tld.zig

@@ -11,12 +11,12 @@ const B = struct {
 const C = struct {
     x: i32,
 
-    fn d(c: &const C) i32 {
+    fn d(c: *const C) i32 {
         return c.x;
     }
 };
 
-fn foo(a: &const A) i32 {
+fn foo(a: *const A) i32 {
     return a.b.c.d();
 }