Disabled the HAVEGE random generator by default

Rationale: The HAVEGE random generator has too many caveats to be a
standard generator that people rely on. The HAVEGE random generator is not
suitable for virtualized environments. In addition the HAVEGE random
generator is dependent on timing and specific processor traits that
cannot be guaranteed by default on compile time.

Our advice: only use HAVEGE as an additional random source for your
entropy pool, never as your primary source.
diff --git a/ChangeLog b/ChangeLog
index ce8f1d9..53a6095 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,6 +1,9 @@
 PolarSSL ChangeLog
 
 = Branch 1.2
+Change
+   * HAVEGE random generator disabled by default
+
 Bugfix
    * Secure renegotiation extension should only be sent in case client
      supports secure renegotiation