Add some inline links to "previous examples"

Fixes #144.

examples/mutexes/mutexes.go

@@ -1,6 +1,6 @@
 // In the previous example we saw how to manage simple
-// counter state using atomic operations. For more complex
-// state we can use a _[mutex](http://en.wikipedia.org/wiki/Mutual_exclusion)_
+// counter state using [atomic operations](atomic-counters).
+// For more complex state we can use a _[mutex](http://en.wikipedia.org/wiki/Mutual_exclusion)_
 // to safely access data across multiple goroutines.
 
 package main

examples/mutexes/mutexes.hash

@@ -1,2 +1,2 @@
-a42e6b574ab2c2bdd38df53d77b9a2f3f3e0b10c
--_LKNceBru
+3ce8467418aa740ea6c930afac3985a943c76311
+kZrod-Rkos