Fix the documentation for RandNormal.

As pointed out by Jim Roseborough, this is the Marsaglia Polar
method and not the Box-Muller method.

Change-Id: Id5332bcd4b4c23a3885cc296729b44eaa5edd0a8

examples/random.h

diff --git a/examples/random.h b/examples/random.h
index 23eb305..0d55b49 100644
--- a/examples/random.h
+++ b/examples/random.h
@@ -44,8 +44,8 @@
   return r / RAND_MAX;
 }
 
-// Box-Muller algorithm for normal random number generation.
-// http://en.wikipedia.org/wiki/Box-Muller_transform
+// Marsaglia Polar method for generation standard normal (pseudo)
+// random numbers http://en.wikipedia.org/wiki/Marsaglia_polar_method
 inline double RandNormal() {
   double x1, x2, w;
   do {