Merge remote-tracking branch 'upstream-public/pr/1861' into development

Add Changelog entry
diff --git a/ChangeLog b/ChangeLog
index d731673..6c02e2f 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -14,6 +14,8 @@
 Changes
    * Copy headers preserving timestamps when doing a "make install".
      Contributed by xueruini.
+   * Allow the forward declaration of public structs. Contributed by Dawid
+     Drozd. Fixes #1215 raised by randombit.
 
 = mbed TLS 2.12.0 branch released 2018-07-25