Add ChangeLog entry. Fixes
mbed TLS ChangeLog (Sorted per branch, date)
+= mbed TLS x.x.x branch released xxxx-xx-xx
+
+Changes
+ * Use (void) when defining functions with no parameters. Contributed by
+ Joris Aerts. #678
+
= mbed TLS 2.4.0 branch released 2016-10-17
Security
