changes: add note about application output formatting differences.

Fixes #13220

Reviewed-by: Tomas Mraz <tomas@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/15168)

CHANGES.md

@@ -134,6 +134,15 @@ OpenSSL 3.0
    Previously (in 1.1.1) they would return -2. For key types that do not have
    parameters then EVP_PKEY_param_check() will always return 1.
 
+ * The output from the command line applications may have minor
+   changes.  These are primarily changes in capitalisation and white
+   space.  However, in some cases, there are additional differences.
+   For example, the DH parameters output from `dhparam` now lists 'P',
+   'Q', 'G' and 'pcounter' instead of 'prime', 'generator', 'subgroup
+   order' and 'counter' respectively.
+
+   *Paul Dale*
+
  * The output from numerous "printing" functions such as X509_signature_print(),
    X509_print_ex(), X509_CRL_print_ex(), and other similar functions has been
    amended such that there may be cosmetic differences between the output