doc/go_faq.html: link to the SPLASH talk near the top

It's a full answer to the first question; let's let readers know that.

R=golang-dev, bradfitz
CC=golang-dev
https://golang.org/cl/12788048

doc/go_faq.html

@@ -55,6 +55,11 @@ By its design, Go proposes an approach for the construction of system
 software on multicore machines.
 </ul>
 
+<p>
+A much more expansive answer to this question is available in the article,
+<a href="http://talks.golang.org/2012/splash.article">Go at Google:
+Language Design in the Service of Software Engineering</a>.
+
 <h3 id="What_is_the_status_of_the_project">
 What is the status of the project?</h3>