title: 'HMAC_CTX' has incomplete type
body: <p>I'm trying to compile a C++ project on Fedora 31 and I receive this error:</p>
  
  <pre><code>[ 66%] Building CXX object proxy_ws/CMakeFiles/proxy_lws.dir/proxy_lws.cpp.o
  In file included from /vagrant/include/libwebsockets.h:600,
                   from /vagrant/proxy_ws/proxy_lws_utils.hpp:12,
                   from /vagrant/proxy_ws/proxy_lws.cpp:18:
  /vagrant/include/libwebsockets/lws-genhash.h:80:18: error: field ‘ctx’ has incomplete type ‘HMAC_CTX’ {aka ‘hmac_ctx_st’}
     80 |         HMAC_CTX ctx;
        |                  ^~~
  In file included from /usr/include/openssl/crypto.h:25,
                   from /usr/include/openssl/comp.h:16,
                   from /usr/include/openssl/ssl.h:17,
                   from /vagrant/include/libwebsockets.h:250,
                   from /vagrant/proxy_ws/proxy_lws_utils.hpp:12,
                   from /vagrant/proxy_ws/proxy_lws.cpp:18:
  /usr/include/openssl/ossl_typ.h:104:16: note: forward declaration of ‘HMAC_CTX’ {aka ‘struct hmac_ctx_st’}
    104 | typedef struct hmac_ctx_st HMAC_CTX;
        |                ^~~~~~~~~~~
  </code></pre>
  
  <p>Any ideas on how to fix it?</p>