Verifier now accepts multiple errors (fixes #387). (#452)

* Verifier now accepts multiple errors (fixes #387).

lib/frontend/src/lib.rs

@@ -120,9 +120,8 @@
 //!     let flags = settings::Flags::new(settings::builder());
 //!     let res = verify_function(&func, &flags);
 //!     println!("{}", func.display(None));
-//!     match res {
-//!         Ok(_) => {}
-//!         Err(err) => panic!("{}", err),
+//!     if let Err(errors) = res {
+//!         panic!("{}", errors);
 //!     }
 //! }
 //! ```