Build failed on gcc 7.1.0

[amoghe]

Apart from the previously mentioned issue in detecting gcc version (see #22), the build fails due to this:

crypto/crypto_utils.c: In function 'HMAC_CTX_copy':
crypto/crypto_utils.c:109:28: error: dereferencing pointer to incomplete type 'HMAC_CTX {aka struct hmac_ctx_st}'
  if (!EVP_MD_CTX_copy(&dctx->i_ctx, &sctx->i_ctx))
                            ^~
crypto/crypto_utils.c: In function 'PKCS5_PBKDF2_HMAC':
crypto/crypto_utils.c:131:11: error: storage size of 'hctx' isn't known
  HMAC_CTX hctx;
           ^~~~
crypto/crypto_utils.c:137:2: warning: implicit declaration of function 'HMAC_CTX_init'; did you mean 'HMAC_CTX_new'? [-Wimplicit-function-declaration]
  HMAC_CTX_init(&hctx);
  ^~~~~~~~~~~~~
  HMAC_CTX_new
crypto/crypto_utils.c:173:2: warning: implicit declaration of function 'HMAC_CTX_cleanup'; did you mean 'HMAC_CTX_get_md'? [-Wimplicit-function-declaration]
  HMAC_CTX_cleanup(&hctx);
  ^~~~~~~~~~~~~~~~
  HMAC_CTX_get_md
crypto/crypto_utils.c:131:11: warning: unused variable 'hctx' [-Wunused-variable]
  HMAC_CTX hctx;
           ^~~~
crypto/crypto_utils.c: In function 'hmac_init':
crypto/crypto_utils.c:485:47: error: invalid application of 'sizeof' to incomplete type 'HMAC_CTX {aka struct hmac_ctx_st}'
    HMAC_CTX *ctx = (HMAC_CTX *)malloc(sizeof (HMAC_CTX));
                                               ^~~~~~~~
crypto/crypto_utils.c:491:37: error: invalid application of 'sizeof' to incomplete type 'HMAC_CTX {aka struct hmac_ctx_st}'
    ctx = (HMAC_CTX *)malloc(sizeof (HMAC_CTX));
                                     ^~~~~~~~
crypto/crypto_utils.c:518:47: error: invalid application of 'sizeof' to incomplete type 'HMAC_CTX {aka struct hmac_ctx_st}'
    HMAC_CTX *ctx = (HMAC_CTX *)malloc(sizeof (HMAC_CTX));
                                               ^~~~~~~~
crypto/crypto_utils.c:524:37: error: invalid application of 'sizeof' to incomplete type 'HMAC_CTX {aka struct hmac_ctx_st}'
    ctx = (HMAC_CTX *)malloc(sizeof (HMAC_CTX));
                                     ^~~~~~~~
Makefile:305: recipe for target 'crypto/crypto_utils.o' failed
make: *** [crypto/crypto_utils.o] Error 1

To reproduce this, I used a container:

docker pull gcc
docker run -it gcc /bin/bash
# Download tarball from https://storage.googleapis.com/google-code-archive-downloads/v2/code.google.com/pcompress/pcompress-2.4.tar.bz2
# This is 2.4, from several years ago -- maybe I just need to try with HEAD
apt-get install yasm
./config && make