doc/go1.2: link to cgo documentation

I know it's linked in the previous sentence, but this new link is where I want it to be while reading this sentence.

R=golang-dev, bradfitz
CC=golang-dev
https://golang.org/cl/21770043

doc/go1.2.html

@@ -190,8 +190,8 @@ include new stack management technology that should address the problem better.
 
 <p>
 The <a href="/cmd/cgo/"><code>cgo</code></a> command will now invoke the C++
-compiler to build any pieces of the linked-to library that are written in C++; the
-documentation has more detail.
+compiler to build any pieces of the linked-to library that are written in C++;
+<a href="/cmd/cgo/">the documentation</a> has more detail.
 </p>
 
 <h3 id="go_tools_godoc">Godoc and vet moved to the go.tools subrepository</h3>