crypto: hash: add hash driver framework

1) makes the public APIs in hash-nettle/gcrypt/glib static,
   and rename them with "nettle/gcrypt/glib" prefix.

2) introduces hash framework, including QCryptoHashDriver
   and new public APIs.

Reviewed-by: Gonglei <arei.gonglei@huawei.com>
Signed-off-by: Longpeng(Mike) <longpeng2@huawei.com>
Signed-off-by: Daniel P. Berrange <berrange@redhat.com>

crypto/hashpriv.h

@@ -0,0 +1,31 @@
+/*
+ * QEMU Crypto hash driver supports
+ *
+ * Copyright (c) 2017 HUAWEI TECHNOLOGIES CO., LTD.
+ *
+ * Authors:
+ *    Longpeng(Mike) <longpeng2@huawei.com>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or
+ * (at your option) any later version.  See the COPYING file in the
+ * top-level directory.
+ *
+ */
+
+#ifndef QCRYPTO_HASHPRIV_H
+#define QCRYPTO_HASHPRIV_H
+
+typedef struct QCryptoHashDriver QCryptoHashDriver;
+
+struct QCryptoHashDriver {
+    int (*hash_bytesv)(QCryptoHashAlgorithm alg,
+                       const struct iovec *iov,
+                       size_t niov,
+                       uint8_t **result,
+                       size_t *resultlen,
+                       Error **errp);
+};
+
+extern QCryptoHashDriver qcrypto_hash_lib_driver;
+
+#endif