Add test for cross-crate Self

Author: jyn514

Diff for: src/test/rustdoc/intra-doc-crate/auxiliary/self.rs

@@ -0,0 +1,7 @@
+#![crate_name = "cross_crate_self"]
+pub struct S;
+
+impl S {
+    /// Link to [Self::f]
+    pub fn f() {}
+}

Diff for: src/test/rustdoc/intra-doc-crate/self.rs

@@ -0,0 +1,6 @@
+// aux-build:self.rs
+
+extern crate cross_crate_self;
+
+// @has self/struct.S.html '//a[@href="../self/struct.S.html#method.f"]' "Self::f"
+pub use cross_crate_self::S;