curl_ntlm_core: don't complain but #include OpenSSL header if needed

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>

lib/curl_ntlm_core.h

@@ -29,10 +29,7 @@
 #if !defined(USE_WINDOWS_SSPI) || defined(USE_WIN32_CRYPTO)
 
 #ifdef USE_OPENSSL
-#  if !defined(OPENSSL_VERSION_NUMBER) && \
-      !defined(HEADER_SSL_H) && !defined(HEADER_MD5_H)
-#    error "curl_ntlm_core.h shall not be included before OpenSSL headers."
-#  endif
+#  include <openssl/ssl.h>
 #endif
 
 /* Define USE_NTRESPONSES in order to make the type-3 message include