Indenting for modules

rustfmt now bootstraps!

src/visitor.rs

@@ -135,6 +135,11 @@ impl<'a, 'v> visit::Visitor<'v> for FmtVisitor<'a> {
                 visit::walk_item(self, item);
                 self.block_indent -= TAB_SPACES;
             }
+            ast::Item_::ItemMod(_) => {
+                self.block_indent += TAB_SPACES;
+                visit::walk_item(self, item);
+                self.block_indent -= TAB_SPACES;
+            }
             _ => {
                 visit::walk_item(self, item);
             }

tests/idem/mod-1.rs

@@ -0,0 +1,15 @@
+// Deeply indented modules.
+
+mod foo {
+    mod bar {
+        mod baz {
+            fn foo() {
+                bar()
+            }
+        }
+    }
+
+    mod qux {
+
+    }
+}