LibreSSL does not provide EVP_sha512_256()

Index: src/ne_openssl.c
--- src/ne_openssl.c.orig
+++ src/ne_openssl.c
@@ -1122,7 +1122,6 @@ static const EVP_MD *hash_to_md(unsigned int flags)
     case NE_HASH_SHA256: return EVP_sha256();
 #ifdef HAVE_OPENSSL11
     case NE_HASH_SHA512: return EVP_sha512();
-    case NE_HASH_SHA512_256: return EVP_sha512_256();
 #endif
     default: break;
     }
