Fix bug with extension-less ServerHello

https://tls.mbed.org/discussions/bug-report-issues/server-hello-parsing-bug

in_hslen include the length of the handshake header. (We might want to change
that in the future, as it is a bit annoying.)

ChangeLog

diff --git a/ChangeLog b/ChangeLog
index 77a5b9d..184d31d 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -6,6 +6,8 @@
    * Fix segfault in the benchmark program when benchmarking DHM.
    * Fix build error with CMake and pre-4.5 versions of GCC (found by Hugo
      Leisink).
+   * Fix bug when parsing a ServerHello without extensions (found by David
+     Sears).
 
 = mbed TLS 2.0.0 released 2015-07-13