Remove special case for statement NodeId assignment

We now let `noop_flat_map_stmt` assign `NodeId`s (via `visit_id`),
just as we do for other AST nodes.

compiler/rustc_expand/src/lib.rs

@@ -7,6 +7,7 @@
 #![feature(proc_macro_internals)]
 #![feature(proc_macro_span)]
 #![feature(try_blocks)]
+#![recursion_limit = "256"]
 
 #[macro_use]
 extern crate rustc_macros;