Add Changelog entry for CA list suppression

ChangeLog

diff --git a/ChangeLog b/ChangeLog
index 7a88f2f..7117d40 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -2,6 +2,11 @@
 
 = mbed TLS 2.x.x branch released xxxx-xx-xx
 
+Feature
+   * Add a new configuration option to 'mbedtls_ssl_config' to enable
+     suppressing the CA list in Certificate Request messages. The default
+     behaviour has not changed, namely every configured CAs name is included.
+
 Bugfix
    * Remove macros from compat-1.3.h that correspond to deleted items from most
      recent versions of the library. Found by Kyle Keen.