Merge of fix for IOTSSL-481 - Double free

Potential double free in mbedtls_ssl_conf_psk()
diff --git a/ChangeLog b/ChangeLog
index ca2e717..67da281 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -25,6 +25,9 @@
    * Fix possible heap buffer overflow in base64_encoded() when the input
      buffer is 512MB or larger on 32-bit platforms. Found by Guido Vranken,
      Intelworks. Not trigerrable remotely in TLS.
+   * Fix potential double-free if mbedtls_conf_psk() is called repeatedly on
+     the same mbedtls_ssl_config object and memory allocation fails. Found by
+     Guido Vranken, Intelworks. Cannot be forced remotely.
 
 Changes
    * Added checking of hostname length in mbedtls_ssl_set_hostname() to ensure