Relative link to local types in builtin types doc
These links work for locally rendered offline documentation.
diff --git a/src/lib.rs b/src/lib.rs
index 74e103a..304a87a 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -308,9 +308,9 @@
//! <tr><td>String</td><td>rust::String</td><td></td></tr>
//! <tr><td>&str</td><td>rust::Str</td><td></td></tr>
//! <tr><td>&[u8]</td><td>rust::Slice<uint8_t></td><td><sup><i>arbitrary &[T] not implemented yet</i></sup></td></tr>
-//! <tr><td><a href="https://docs.rs/cxx/0.2/cxx/struct.CxxString.html">CxxString</a></td><td>std::string</td><td><sup><i>cannot be passed by value</i></sup></td></tr>
+//! <tr><td><a href="struct.CxxString.html">CxxString</a></td><td>std::string</td><td><sup><i>cannot be passed by value</i></sup></td></tr>
//! <tr><td>Box<T></td><td>rust::Box<T></td><td><sup><i>cannot hold opaque C++ type</i></sup></td></tr>
-//! <tr><td><a href="https://docs.rs/cxx/0.2/cxx/struct.UniquePtr.html">UniquePtr<T></a></td><td>std::unique_ptr<T></td><td><sup><i>cannot hold opaque Rust type</i></sup></td></tr>
+//! <tr><td><a href="struct.UniquePtr.html">UniquePtr<T></a></td><td>std::unique_ptr<T></td><td><sup><i>cannot hold opaque Rust type</i></sup></td></tr>
//! <tr><td>fn(T, U) -> V</td><td>rust::Fn<V(T, U)></td><td><sup><i>only passing from Rust to C++ is implemented so far</i></sup></td></tr>
//! <tr><td>Result<T></td><td>throw/catch</td><td><sup><i>allowed as return type only</i></sup></td></tr>
//! </table>