Add test certificate for bitstring in DN

ChangeLog

@@ -5,6 +5,8 @@ mbed TLS ChangeLog (Sorted per branch, date)
 Security
 
 Features
+   * Add support for bit strings in X.509 names (request by Fredrik Axelsson).
+   * Add support for id-at-uniqueIdentifier in X.509 names.
    * Add support for overriding snprintf() (except on Windows) and exit() in
      the platform layer.
    * Add an option to use macros instead of function pointers in the platform