feat(ssl): Restructure ssl folder

Put mbedtls, axtls, openssl to ssl, also add kconfig to choose ssl library.
Default use mbedtls.

components/ssl/openssl/include/internal/ssl_cert.h

@@ -0,0 +1,55 @@
+// Copyright 2015-2016 Espressif Systems (Shanghai) PTE LTD
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef _SSL_CERT_H_
+#define _SSL_CERT_H_
+
+#ifdef __cplusplus
+ extern "C" {
+#endif
+
+#include "ssl_types.h"
+
+/**
+ * @brief create a certification object include private key object according to input certification
+ *
+ * @param ic - input certification point
+ *
+ * @return certification object point
+ */
+CERT *__ssl_cert_new(CERT *ic);
+
+/**
+ * @brief create a certification object include private key object
+ *
+ * @param none
+ *
+ * @return certification object point
+ */
+CERT* ssl_cert_new(void);
+
+/**
+ * @brief free a certification object
+ *
+ * @param cert - certification object point
+ *
+ * @return none
+ */
+void ssl_cert_free(CERT *cert);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif