Fix build script reference problem

Reviewed By: pquerna@apache.org

Test Plan: build w/o libevent installed


git-svn-id: https://svn.apache.org/repos/asf/incubator/thrift/trunk@665081 13f79535-47bb-0310-9956-ffa450edef68
diff --git a/lib/cpp/aclocal/ax_event_base.m4 b/lib/cpp/aclocal/ax_event_base.m4
index 4418350..9d5c525 100644
--- a/lib/cpp/aclocal/ax_event_base.m4
+++ b/lib/cpp/aclocal/ax_event_base.m4
@@ -70,7 +70,7 @@
 	fi
 
 	if test "$succeeded" != "yes" ; then
-            AC_MSG_ERROR([[We could not detect the event libraries (version $event_lib_version_req_shorten or higher). If you have a staged event library (still not installed) please specify \$EVENT_ROOT in your environment and do not give a PATH to --with-event option.  If you are sure you have event installed, then check your version number looking in <event/version.hpp>. See http://randspringer.de/event for more documentation.]])
+            AC_MSG_ERROR([[We could not detect the event libraries (version $event_lib_version_req_shorten or higher). If you have a staged event library (still not installed) please specify \$EVENT_ROOT in your environment and do not give a PATH to --with-event option.  If you are sure you have event installed, then check your version number looking in <event.h>. See http://www.monkey.org/~provos/libevent/ for more documentation.]])
 	else
             AC_SUBST(EVENT_CPPFLAGS)
 	    AC_SUBST(EVENT_LDFLAGS)