Commit 9fdcc21 made lots of constification changes. One of those was to make the parameter of EVP_PKEY_CTX_dup() a const. That in itself is fine and is API compatible, but that function calls the "copy" function of the underlying EVP_PKEY_METHOD. Therefore that commit also changed the function pointer parameter to EVP_PKEY_meth_set_copy:

 void EVP_PKEY_meth_set_copy(EVP_PKEY_METHOD *pmeth,
                             int (*copy) (EVP_PKEY_CTX *dst,
-                                         EVP_PKEY_CTX *src));
+                                         const EVP_PKEY_CTX *src));

This change is not API compatible and so represents an API break with 1.1.1 (something we are explicitly trying to avoid as much as possible).

Should we revert this aspect of the change (not sure what the consequences of doing that might be since this change was made for a reason)?