Fix undefined shifts

- in x509_profile_check_pk_alg
- in x509_profile_check_md_alg
- in x509_profile_check_key

and in ssl_cli.c : unsigned char gets promoted to signed integer
diff --git a/ChangeLog b/ChangeLog
index 8ebe9bb..189a071 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -20,6 +20,8 @@
 Bugfix
    * Fix an issue with MicroBlaze support in bn_mul.h which was causing the
      build to fail. Found by zv-io. Fixes #1651.
+   * Fix undefined shifts with negative values in certificates parsing
+     (found by Catena cyber using oss-fuzz)
 
 Changes
    * Support TLS testing in out-of-source builds using cmake. Fixes #1193.