Fix link to Boost.Coroutine library.

asio/src/doc/examples.qbk

diff --git a/asio/src/doc/examples.qbk b/asio/src/doc/examples.qbk
index c34f7f6..f147f44 100644
--- a/asio/src/doc/examples.qbk
+++ b/asio/src/doc/examples.qbk
@@ -302,7 +302,7 @@
 [heading Spawn]
 
 Example of using the asio::spawn() function, a wrapper around the
-[@www.boost.org/doc/libs/release/libs/coroutine/index.html Boost.Coroutine]
+[@http://www.boost.org/doc/libs/release/libs/coroutine/index.html Boost.Coroutine]
 library, to implement a chain of asynchronous operations using stackful
 coroutines.
 
@@ -399,7 +399,7 @@
 [heading Spawn]
 
 Example of using the asio::spawn() function, a wrapper around the
-[@www.boost.org/doc/libs/release/libs/coroutine/index.html Boost.Coroutine]
+[@http://www.boost.org/doc/libs/release/libs/coroutine/index.html Boost.Coroutine]
 library, to implement a chain of asynchronous operations using stackful
 coroutines.