title: error: field 'ctx' has incomplete type EVP_CIPHER_CTX
body: <p>Problem: I need to install Cepstral (tts engine) into Freeswitch running Debian 8. Freeswitch is already up and running, but I needed to build it from source in order for it create the mod_cepstral module. </p>
  
  <p>When I run <code>make</code> this is the error I get:</p>
  
  <pre><code>In file included from ./crypto/include/prng.h:17:0,
                   from ./crypto/include/crypto_kernel.h:50,
                   from ./include/srtp.h:53,
                   from srtp/srtp.c:46:
  ./crypto/include/aes_icm_ossl.h:66:20: error: field ‘ctx’ has incomplete type
       EVP_CIPHER_CTX ctx;
                      ^~~
  In file included from srtp/srtp.c:50:0:
  ./crypto/include/aes_gcm_ossl.h:58:18: error: field ‘ctx’ has incomplete type
     EVP_CIPHER_CTX ctx;
                    ^~~
  Makefile:646: recipe for target 'srtp.lo' failed
  make[1]: *** [srtp.lo] Error 1
  make[1]: Leaving directory '/usr/src/freeswitch/libs/srtp'
  Makefile:3931: recipe for target 'libs/srtp/libsrtp.la' failed
  make: *** [libs/srtp/libsrtp.la] Error 2
  </code></pre>
  
  <p>I have been scouring the internet for solutions, but I am not a developer and this is way over my head. Any help would be appreciated. </p>