Added ssl_handshake_step() to allow single stepping the handshake
process

Single stepping the handshake process allows for better support of
non-blocking network stacks and for getting information from specific
handshake messages if wanted.
diff --git a/ChangeLog b/ChangeLog
index 701f86b..f590069 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,6 +1,9 @@
 PolarSSL ChangeLog
 
 = Version Master
+Changes
+   * Added ssl_handshake_step() to allow single stepping the handshake process
+
 Bugfix
    * Memory leak when using RSA_PKCS_V21 operations fixed
    * Handle future version properly in ssl_write_certificate_request()