Add Body AST item and visit_body in visitor

Signed-off-by: Alek Ratzloff <alekratz@gmail.com>

src/syn/visit.rs

@@ -11,6 +11,7 @@ pub trait DefaultAccept<V: Visit + ?Sized> {
 pub trait Visit {
     type Out;
 
+    fn visit_body(&mut self, body: &Body) -> Self::Out;
     fn visit_stmt(&mut self, stmt: &Stmt) -> Self::Out;
     fn visit_assign_stmt(&mut self, assign: &AssignStmt) -> Self::Out;
     fn visit_lhs_expr(&mut self, lhs_expr: &LhsExpr) -> Self::Out;