rustdoc-search: add index of borrow references

tests/rustdoc-js/reference.rs

@@ -0,0 +1,32 @@
+#![feature(extern_types)]
+
+pub fn pinky(input: &usize, manage: usize) {
+    unimplemented!()
+}
+
+pub struct Thumb;
+
+impl Thumb {
+    pub fn up(&self, finger: Thumb) { unimplemented!() }
+}
+
+pub enum Index {}
+
+impl Index {
+    pub fn point(self, data: &Index) { unimplemented!() }
+}
+
+pub union Ring {
+    magic: u32,
+    marriage: f32,
+}
+
+impl Ring {
+    pub fn wear(&mut self, extra: &Ring) { unimplemented!() }
+}
+
+extern "C" {
+    pub type Middle;
+}
+
+pub fn show(left: &&mut Middle, right: &mut &Middle) { unimplemented!() }