Abstract EVP cipher context creation

The EVP_CIPHER_CTX is now created inside a wrapper function to add support
for OpenSSL 1.1. Also fixed improper use of the EVP_CIPHER_CTX internals
in binlogrouter.

server/core/encryption.c

@@ -0,0 +1,37 @@
+/*
+ * Copyright (c) 2016 MariaDB Corporation Ab
+ *
+ * Use of this software is governed by the Business Source License included
+ * in the LICENSE.TXT file and at www.mariadb.com/bsl11.
+ *
+ * Change Date: 2020-01-01
+ *
+ * On the date above, in accordance with the Business Source License, use
+ * of this software will be governed by version 2 or later of the General
+ * Public License.
+ */
+
+#include <maxscale/cdefs.h>
+
+#include <maxscale/alloc.h>
+#include <maxscale/encryption.h>
+
+EVP_CIPHER_CTX* mxs_evp_cipher_ctx_alloc()
+{
+#ifdef OPENSSL_1_1
+    return EVP_CIPHER_CTX_new();
+#else
+    EVP_CIPHER_CTX* rval = (EVP_CIPHER_CTX*)MXS_MALLOC(sizeof(*rval));
+    EVP_CIPHER_CTX_init(rval);
+    return rval;
+#endif
+}
+
+void mxs_evp_cipher_ctx_free(EVP_CIPHER_CTX* ctx)
+{
+#ifdef OPENSSL_1_1
+    EVP_CIPHER_CTX_free(ctx);
+#else
+    MXS_FREE(ctx);
+#endif
+}