Rename issue-\d+.rs tests to have meaningful names

tests/rustdoc/doc-hidden-method-13698.rs

@@ -0,0 +1,18 @@
+// aux-build:issue-13698.rs
+// ignore-cross-compile
+
+#![crate_name="issue_13698"]
+
+extern crate issue_13698;
+
+pub struct Foo;
+// @!has issue_13698/struct.Foo.html '//*[@id="method.foo"]' 'fn foo'
+impl issue_13698::Foo for Foo {}
+
+pub trait Bar {
+    #[doc(hidden)]
+    fn bar(&self) {}
+}
+
+// @!has issue_13698/struct.Foo.html '//*[@id="method.bar"]' 'fn bar'
+impl Bar for Foo {}