Fix non compliance SSLv3 in server extension handling.

The server code parses the client hello extensions even when the
protocol is SSLv3 and this behaviour is non compliant with rfc6101.
Also the server sends extensions in the server hello and omitting
them may prevent interoperability problems.
diff --git a/ChangeLog b/ChangeLog
index 3b32873..d9fce92 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -34,6 +34,8 @@
    * Disabled SSLv3 in the default configuration.
    * Optimized mbedtls_mpi_zeroize() for MPI integer size. (Fix by Alexey
      Skalozub).
+   * Fix non-compliance server extension handling. Extensions for SSLv3 are now
+     ignored, as required by RFC6101.
 
 = mbed TLS 2.2.1 released 2016-01-05