Fix some markdown issues.

Work around some cases where the old markdown parser differs from the
new Pulldown parser for the documentation.

lib/cretonne/src/result.rs

@@ -23,10 +23,10 @@ pub enum CtonError {
 
     /// An implementation limit was exceeded.
     ///
-    /// Cretonne can compile very large and complicated functions, but the implementation has
-    /// limits that cause compilation to fail when they are exceeded.
+    /// Cretonne can compile very large and complicated functions, but the [implementation has
+    /// limits][limits] that cause compilation to fail when they are exceeded.
     ///
-    /// See http://cretonne.readthedocs.io/en/latest/langref.html#implementation-limits
+    /// [limits]: http://cretonne.readthedocs.io/en/latest/langref.html#implementation-limits
     ImplLimitExceeded,
 
     /// The code size for the function is too large.