Fix redefinition of macro ssl_set_bio

Fix redefinition of macro ssl_set_bio to undefined symbol
mbedtls_ssl_set_bio_timeout in compat-1.3.h.
diff --git a/ChangeLog b/ChangeLog
index f96786d..b5f8812 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,11 @@
 mbed TLS ChangeLog (Sorted per branch, date)
 
+= mbed TLS x.x.x branch released xxxx-xx-xx
+
+Bugfix
+   * Fix redefinition of macro ssl_set_bio to undefined symbol
+     mbedtls_ssl_set_bio_timeout in compat-1.3.h. #673
+
 = mbed TLS 2.4.0 branch released 2016-10-17
 
 Security